Methods and electrode apparatus to achieve a closure of a layered tissue defect

ABSTRACT

Methods for treating anatomic tissue defects such as a patent foramen ovale generally involve positioning a distal end of a catheter device at the site of the defect, exposing a housing and energy transmission member from the distal end of the catheter, engaging the housing with tissues at the site of the defect, applying suction or other approximating tool to the tissue via the housing to bring the tissue together, and applying energy to the tissue with the energy transmission member or to deliver a clip or fixation device to substantially close the defect. Apparatus generally include a catheter body, a housing extending from a distal end of the catheter body for engaging tissue at the site of the defect, and further adapted to house a fusing or fixation device such as an energy transmission member adjacent a distal end of the housing, or a clip or fixation delivery element.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 11/403,052 filed Apr.11, 2006, which is also the non-provisional of U.S. Ser. No. 60/670,535,filed Apr. 11, 2005, the entire contents of both of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention generally relates to medical devices and methods. Morespecifically, the invention relates to positioning closure devices,including energy based devices and methods for treatment of anatomicdefects in human tissue, such as a patent foramen ovale (PFO), atrialseptal defect (ASD), ventricular septal defect (VSD), patent ductusarteriosis (PDA), left atrial appendages (LAA), blood vessel walldefects and other defects having layered and apposed tissue structures.

The following is an example of how one particular type of anatomicaldefect, a PFO, is formed. Fetal blood circulation is very different fromadult circulation. Because fetal blood is oxygenated by the placenta,rather than the fetal lungs, blood is generally shunted past the lungsto the peripheral tissues through a number of vessels and foramens thatremain patent (i.e., open) during fetal life and typically close shortlyafter birth. For example, fetal blood passes directly from the rightatrium through the foramen ovale into the left atrium, and a portion ofblood circulating through the pulmonary artery trunk passes through theductus arteriosus to the aorta. This fetal circulation is shown in FIG.1.

At birth, as a newborn begins breathing, blood pressure in the leftatrium rises above the pressure in the right atrium. In most newborns, aflap of tissue closes the foramen ovale and heals together. Inapproximately 20,000 babies born each year in the U.S., the flap oftissue is missing, and the hole remains open as an atrial septal defect(ASD). In a more significant percentage of the population (estimatesrange from 5% to 20% of the entire population), the flap is present butdoes not heal together. This condition is known as a patent foramenovale (PFO). Whenever the pressure in the right atrium rises above thatin the left atrium, blood pressure can push this patent channel open,allowing blood to flow from the right atrium to the left atrium. Bloodshunting also occurs in a patent ductus arteriosis (PDA), where atubular communication exists between the pulmonary artery and the aorta.The PDA typically closes shortly after birth.

Patent foramen ovale has long been considered a relatively benigncondition, since it typically has little effect on the body'scirculation. More recently, however, it has been found that asignificant number of strokes may be caused at least in part by PFOs. Insome cases, a stroke may occur because a PFO allows blood containingsmall thrombi to flow directly from the venous circulation to thearterial circulation and into the brain, rather than flowing to thelungs where the thrombi can become trapped and gradually dissolved. Inother cases, a thrombus might form in the patent channel of the PFOitself and become dislodged when the pressures cause blood to flow fromthe right atrium to the left atrium. It has been estimated that patientswith PFOs who have already had cryptogenic strokes may have a risk ofhaving another stroke.

Further research is currently being conducted into the link between PFOand stroke. At the present time, if someone with a PFO has two or morestrokes, the healthcare system in the United States may reimburse asurgical or other interventional procedure to definitively close thePFO. It is likely, however, that a more prophylactic approach would bewarranted to close PFOs to prevent the prospective occurrence of astroke. The cost and potential side-effects and complications of such aprocedure must be low, however, since the event rate due to PFOs isrelatively low. In younger patients, for example, PFOs sometimes closeby themselves over time without any adverse health effects.

Another highly prevalent and debilitating condition, chronic migraineheadache, has also been linked with PFO. Although the exact link has notyet been explained, PFO closure has been shown to eliminate orsignificantly reduce migraine headaches in many patients. Again,prophylactic PFO closure to treat chronic migraine headaches might bewarranted if a relatively non-invasive procedure were available.

Currently available interventional therapies for defect closure aregenerally fairly invasive and/or have potential drawbacks. One strategyis simply to close a defect during open heart surgery for anotherpurpose, such as heart valve surgery. This can typically be achieved viaa simple procedure such as placing a stitch or two across the defectwith vascular suture. Performing open heart surgery purely to close anasymptomatic PFO or even a very small ASD, however, would be very hardto justify.

A number of interventional devices for closing defects percutaneouslyhave also been proposed and developed. Most of these devices are thesame as or similar to ASD closure devices. They are typically“clamshell” or “double umbrella” shaped devices which deploy an area ofbiocompatible metal mesh or fabric (ePTFE or Dacron, for example) oneach side of the atrial septum, held together with a central axialelement, to cover the defect. This umbrella then heals into the atrialseptum, with the healing response forming a uniform layer of tissue or“pannus” over the device. Such devices have been developed, for example,by companies such as Nitinol Medical Technologies, Inc. (Boston, Mass.)and AGA Medical, Inc. (White Bear Lake, Minn.). U.S. Pat. No. 6,401,720describes a method and apparatus for thoracoscopic intracardiacprocedures which may be used for treatment of PFO.

Although available devices may work well in some cases, they also face anumber of challenges. Relatively frequent causes of complicationsinclude, for example, improper deployment, device embolization into thecirculation and device breakage. In some instances, a deployed devicedoes not heal into the septal wall completely, leaving an exposed tissuewhich may itself be a nidus for thrombus formation. Furthermore,currently available devices are generally complex and expensive tomanufacture, making their use for prophylactic treatment of PFO andother defects impractical. Additionally, currently available devicestypically close a PFO by placing material on either side of the tunnelof the PFO, compressing and opening the tunnel acutely, until bloodclots on the devices and causes flow to stop.

Research into methods and compositions for tissue welding has beenunderway for many years. Of particular interest are technologiesdeveloped by McNally et. al., (as shown in U.S. Pat. No. 6,391,049) andFusion Medical (as shown in U.S. Pat. Nos. 5,156,613; 5,669,934;5,824,015 and 5,931,165). These technologies all disclose energydelivery to tissue solders and patches to join tissue and formanastomoses between arteries, bowel, nerves, etc. Also of interest are anumber of patents by inventor Sinofsky, relating to laser suturing ofbiological materials (e.g., U.S. Pat. Nos. 5,725,522; 5,569,239;5,540,677 and 5,071,417). None of these disclosures, however, showmethods or apparatus suitable for positioning the tissues of an anatomicdefect for welding or for delivering the energy to an anatomic defect tobe welded. These disclosures do not teach methods that would beparticularly useful for welding layered tissue structures such as PFOs,nor do they teach bringing together tissues of a defect such that atissue overlap is created that can then be welded together.

Causing thermal trauma to close a patent foramen ovale has beendescribed in two patent applications by Stambaugh et al. (PCTPublication Nos. WO 99/18870 and WO 99/18871). The intent is toeventually cause scar tissue formation which will close the PFO. Blaeseret al. (U.S. Patent Publication US2003/0208232), describes causingtrauma, or abrading, and holding the abraded tissue in apposition toallow the tissue to heal together. Using such devices and methods, thePFO typically remains patent immediately after the procedure, orabrasion, and only closes sometime later, or is treated and then heldtogether to heal over time. Frequently, scar tissue may fail to form ormay form incompletely, resulting in a still patent PFO.

In addition to PFO, a number of other anatomic tissue defects, such asother ASDs, ventricular septal defects (VSDs), patent ductus arteriosis(PDA), aneurysms and other blood vessel wall defects, atrial appendagesand other naturally occurring cavities within which blood clots canform, and the like cause a number of different health problems (notethat the term “defect” may include a naturally occurring structure thatresults a potential health risk such as the clot forming in the atrialappendage). U.S. Patent Application No. 2004/0098031 (Van der Burg), andU.S. Pat. No. 6,375,668 (Gifford) and U.S. Pat. No. 6,730,108 (VanTassel et al.), the full disclosures of which are incorporated herein byreference, disclose a variety of techniques and devices for treatinganatomic defects. In addition, the inventors of the present inventionhave described a number of improved devices, methods and systems fortreating a PFO, many of which may be adapted for treating other anatomictissue defects as well. For example, related patent applicationsassigned to the assignee of the present invention include U.S. patentapplication Ser. Nos.: Ser. No. 10/665,974 (Attorney Docket No.022128-000300US), filed on Sep. 16, 2003; Ser. No. 10/679,245 (AttorneyDocket No. 022128-000200US), filed Oct. 2, 2003; Ser. No. 10/952,492(Attorney Docket No. 022128-000220US), filed Sep. 27, 2004; Ser. No.10/873,348 (Attorney Docket No. 022128-000210US), filed on Jun. 21,2004; Ser. No. 11/049,791 (Attorney Docket No. 022128-000211US), filedon Feb. 2, 2005; Ser. No. 10/787,532 (Attorney Docket No.022128-000130US), filed Feb. 25, 2004; Ser. No. 10/764,148 (AttorneyDocket No. 022128-000510US), filed Jan. 23, 2004; Ser. No. 10/811,228(Attorney Docket No. 022128-000400US), filed Mar. 26, 2004; and U.S.Provisional Application 60/670/535 (Attorney Docket No.022128-000700US), filed Apr. 11, 2005, the full disclosures of which areincorporated herein by reference.

Despite improvements made thus far, it would be advantageous to haveeven further improved methods, systems, and apparatus for treatinganatomic tissue defects such as PFOs and the other anatomic structuresmentioned above. Ideally, such methods and apparatus would help positiona closure device so that a complete seal of a PFO or other anatomictissue defect can be achieved reliably and in a predictable fashion.Also, such devices and methods would leave no foreign material (or verylittle material) in a patient's heart. Furthermore, such methods andapparatus would preferably be relatively simple to manufacture and use,thus rendering prophylactic treatment of PFO and other tissue defects aviable option. Ideally, such methods and apparatus could also be used ina minimally invasive manner, with low profile for ease of introductioninto the body, while effectively closing the PFO quickly, effectivelyand without causing damage to other portions of the body. When successof the closure procedure can be well predicted, physicians are morelikely to recommend such a procedure prophylacticly. At least some ofthese objectives will be met by the present invention.

BRIEF SUMMARY OF THE INVENTION

The present invention provides apparatus, systems and methods fortreating anatomic defects in human tissues, particularly defectsinvolving tissue layers where it is desired to weld or fuse the layerstogether, such as a patent foramen ovale (PFO). The methods will alsofind use with closing a variety of other defects which may or may notdisplay layered tissue structures, such as atrial septal defects,ventricular septal defects, patent ductus arteriosis, left atrialappendages, blood vessel wall defects, and the like. For the treatmentof PFOs, the apparatus will usually comprise endovascular/intravascularcatheters having an elongate catheter body with a proximal end and adistal end. A housing may be positioned at or near a distal end of thecatheter body, where the housing has an opening for engaging a tissuesurface where the tissue defect may be present. Usually, the housingwill be connectable to a vacuum source to enhance engagement of thehousing against the tissue, and an energy transmission member, such asan electrode, may be positioned at or near the opening in the housing toapply energy to the tissue to effect welding and closure. For purposesof this disclosure, the terms sealing, closing, welding, fusing are usedinterchangeably to describe bringing tissues of a defect together so asto result in a substantial seal e.g. no physiologic leak of biologicalfluid or operator infused fluid across the sealed area. Although avariety of mechanisms may work to achieve this, the sealing or closingof the defect can occur via the presence or absence of a variety ofbiologic processes, some of which may be fusion or lamination of thetissue cells, layers or collagen, expression/combination of factors fromthe tissue that are expressed upon application of energy, denaturationand re-naturation of tissue elements, crosslinking, necrosis or partialnecrosis or other cellular phenomena present at the treatment site uponapplication of the energies described herein, or combinations thereof.

Alternatively, instead of an electrode, the suction housing may beadapted for passage of a closure device such as a clip or fixationelement that may be placed through the tissue of the defect while it isstabilized by the suction housing. The following description will oftenfocus on PFO treatment, but at least many of the inventive embodimentsmay be employed for treating other tissue defects and in other contexts.

In a first aspect of the present invention, an apparatus for fusing alayered tissue structure comprises a catheter body with proximal anddistal ends, a housing on a distal portion of the catheter body and anenergy transmission member associated with the housing. The energytransmission member is configured to distribute energy over apredetermined pattern.

In a second aspect of the present invention, an apparatus for fusing alayered tissue structure comprises a catheter body having both proximaland distal ends, a vacuum housing on a distal portion of the catheterbody and an energy transmission member disposed on or within the vacuumhousing. The energy transmission member also has at least one openingwhich is adapted to receive tissue when a vacuum is applied to thehousing.

In a third aspect of the present invention, a method for fusing apposedlayered tissue structures comprises advancing a closure device at afirst treatment site having apposed layers of tissue, applying energyfrom the closure device to the layers of tissue and controlling theapplied energy to minimize creation of aberrant conductive paths and toenhance fusing at of the layers. The method may further include coolingdown the closure device and the apposed layers to tissue and releasingthe closure device away from the tissue structure. Often the methodincludes a closure device comprising a catheter body having a proximalend and a distal end, a housing on the distal portion of the catheterbody and an energy transmission member associated with the housing isconfigured to deliver energy over a predetermined pattern.

In a fourth aspect of the present invention, a method generally takesthe same form as the method previously described, except here, themethod comprises a catheter body having a proximal and distal end, avacuum housing on a distal portion of the catheter body and an energytransmission member disposed on or within the vacuum housing and havingan opening adapted to receive tissue when a vacuum is applied to thehousing.

In the first four aspects of the present invention, as described above,various embodiments are contemplated. For example, the energytransmission member may be disposed over an opening in the housing andis adapted to allow the housing to appose the layered tissue structure.Often the energy transmission member is collapsible and typically has anactive surface. In some embodiments, the energy transmission member alsohas an inactive surface. A non-conductive mask may be used to define theactive surface which may be variable. The non-conductive mask can beconnected with the active region and forms an insulated region betweenthe housing and the energy transmission member.

Often, the energy transmission member is an electrode, and the geometryof the energy transmission member substantially approximates the layeredtissue structure to be treated. In some embodiments, the layered tissuestructure is a patent foramen ovale (PFO) and the energy transmissionmember can treat PFOs ranging in size from about 1 mm to about 30 mm.The electrode may be adapted to penetrate tissue.

In other embodiments, the energy transmission member comprises a bandwhich can be shaped in a number of ways, including elliptical, circular,rectangular, triangular and combinations thereof. Other patterns for theband include an undulating wave-like pattern and the energy transmissionmember can also comprise a mesh, lobes or a bar. In the case of a bar,the bars have a length and a width and the bar length is often greaterthan the bar width. Also, the bars may have first and second regionswhich are hingedly connected or oppositely charged and adapted todeliver bipolar energy. The oppositely charged regions may alternatate.

In still other embodiments, the bars may interdigitate with one anotheror they may be substantially parallel to each other. The bars maycomprise an opening which can be a slit and the slit width is usuallyless than the bar width. Some embodiments include a guidewire lumendisposed in the catheter body, passing through the housing and the lumenhas an exit port between the bars. A ramp may be employed near thedistal exit port. Often, a vacuum may be applied through the bars whichhave been adapted so that tissue adherence is minimized and also allowsa smooth interface with the layered tissue structure. The bars can alsobe adapted to form an edge from which energy is delivered.

The energy transmission member is usually biased toward a proximalportion of the housing in order to maximize the physical distancebetween the AV node of the human heart and an active portion of theenergy transmission member when it is positioned over the layered tissuestructure for treatment. General features may include coating or platingthe energy transmission member for either enhanced electrical orradiopaque characteristics. Also, a guidewire port may be disposedadjacent to the energy transmission member and a vacuum can be appliedthrough the transmission member. Often, struts in the energytransmission member connect it with the housing, or elastic elementsflexibly connect the two together. Also, a thermocouple may be disposednear the energy transmission member in some embodiments and the housingcan be adapted to allow fluid delivery to the layered tissue structurewhen the housing is apposed with the tissue.

In another aspect of the present invention, an apparatus for fusing alayered tissue structure comprises an elongated catheter body with aproximal and distal end, and an energy transmission member connectedwith the elongated body. The energy transmission member is adapted toappose the layered tissue structure and also adapted to deliver bipolarenergy sufficient to fuse the structure. Often the energy transmissionmember is a collapsible electrode which may be adapted to penetratetissue. The energy transmission member has a geometry whichsubstantially approximates the layered tissue structure to be treatedand can treat a PFO with a size ranging from about 1 mm to about 30 mm.

In another aspect of the present invention, a method is disclosed whichis similar to that previously described, except that in this aspect, theclosure device comprises an elongated catheter body with a proximal anddistal end as well as an energy transmission member. The energytransmission member is connected with the catheter and adapted to apposethe layered tissue structure and fuse the structure upon.

In both aspects of the preceding apparatus and method, the energytransmission member may comprise a ring, a mesh or bars. Often, theapparatus comprises a guidewire lumen axially disposed in the catheterbody with a distal exit port adjacent to the energy transmission member.A ramp may be located near the distal exit port and a vacuum may beapplied through the energy transmission member. The energy transmissionmember is also adapted to minimize adherence with tissue. It also may bebiased toward a proximal portion of the catheter body in order tomaximize the physical distance between the AV node of the heart and theenergy transmission member when it is positioned adjacent to the layeredtissue structure to be treated. Optionally, the energy transmissionmember may be coated or plated for enhanced electrical characteristicsor radiopacity. Often, a vacuum is applied through the energytransmission member and a thermocouple may be adjacent to the energytransmission member.

In another aspect of the present invention, a system for fusing layeredtissue structure comprises a treatment catheter having an energytransmission member adapted to deliver energy deliver energy to thelayered tissue structures and a controller connected to the treatmentcatheter. The controller is programmed to vary an energy deliveryparameter from the energy transmission member to the layered tissuestructure to minimize creation of aberrant conductive paths and enhancefusing of adjacent tissue layers in the layered tissue structure.

The controller can be programmed to vary at least one parameter such aspower, pulse rate, frequency and duration. The energy delivery parameteris typically varied in response to an algorithm which may depend upon atissue response parameter. The system often includes one or more sensorsfor measuring a tissue response parameter while the size of the energytransmission member and/or the amount of energy delivered by thecontroller are selected to create a weld lesion having an effective sizein the range from about 5 mm² to 90 mm². In the case of a patent foramenovale, the size of the energy transmission member and/or the amount ofenergy delivered by the controller are selected to create a weld lesionadequate to treat a PFO ranging in size from about 1 mm to about 30 mm.

In another aspect of the present invention, a method for fusing apposedlayered tissue structures comprises applying energy to the layeredtissue structure and controlling the applied energy to minimize creationof aberrant conductive paths and enhance fusing of adjacent tissuelayers in the tissue structure. Controlling the energy typicallyinvolves varying over time at least one parameter such as power, pulserate, frequency, rate of increase, rate of decrease or duration.

Typically, the power parameter is varied at least partially in responseto an algorithm which may be dependent upon a tissue response parameter.The energy is also controlled to create a weld lesion having apredetermined size, typically in the range of 2 mm² to 400 mm², andoften in the range of 5 mm² to 90 mm². Power is usually increased ordecreased during a portion of the treatment cycle. If a tissue responseparameter is used to control the power parameter, common tissueresponses include tissue temperature, impedance and moisture.

The method also comprises controlling power by applying power at aninitial level of P₀, increasing power to a higher level of P₁ over atime period of t₁ and then terminating power after a time period t₂ ifno impedance spike occurs. The method may further comprise reducing orterminating power if an impedance spike occurs, reapplying power at alower level P₂ over a time period t₃ and terminating the reapplied powerif an impedance spike occurs. The method also can comprise controllingpower by applying power at an initial level of P₀ and decreasing powerif an impedance spike occurs. Power may be decreased if the impedancespike is observed within a predetermined time period, and power isterminated after a predetermined cumulative treatment time has passed.Other treatment parameters which may be used to control the procedureare selected based on patient characteristics and may include tissuecharacteristics and the nature of the defect being treated, which can bea patent foramen ovale.

In still another aspect of the present invention, a method for fusingapposed layered tissue structures comprises applying power to theapposed layered tissue structure an initial level P₀, measuring tissueimpedance including initial impedance Z₀ and increasing power by anamount k to a higher level after a given duration of time t₁ until amaximum power level P_(max) is obtained. Power application is terminatedif an impedance spike occurs and power has been applied for a givenduration of time t₂ or longer.

Additional steps comprise temporarily stopping application of power ifan impedance spike occurs and power has been applied for less than agiven duration of time t₂ and re-applying power to the tissue structureat a power level P₁ lower than P₀, if total power delivery time is lessthan t₃, where t₃ is less than t₂. Power may be increased by an amount 2k if impedance has not exceeded its minimum value Z₀ by a given amount rafter a time t₄, where t₄ is greater than t₁.

Additionally, the method may comprise increasing power by another amount2 k if impedance has not exceeded its minimum value Z₀ by a given amountr after a time t₄. Power application is terminated when an impedancespike occurs and power has been applied for a given duration of time t₂or longer. Power is also stopped, temporarily if an impedance spikeoccurs and power has been applied for less than a given duration of timet₂. Power is then reapplied to the tissue structure at a power level P₁,and lower than P₀, if total power delivery time is less than t₃, wheret₃ is less than t₂.

The method further comprises applying power at a level equal to P₁+2 kwhen total power application time prior to decreasing power to P₁exceeds time t₃. Power is increased if impedance has not exceeded itsminimum value after power was decreased to P₁ by r after a time t₄, andpower is terminated if an impedance spike occurs and power has beenapplied for a given duration of time t₂ or longer. Again, power may betemporarily stopped if an impedance spike occurs and power has beenapplied for less than a given duration of time t₂. Power is thenre-applied to the tissue at a power level selected from the groupconsisting of P₁, P₁+2 k and P₁+4 k. Again, if an impedance spikeoccurs, power application is terminated. In all cases, power applicationis terminated after application of power for a maximum time t_(max).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the anatomy of fetal circulation, including a PFO andPDA.

FIGS. 2A-2I show various anatomies of a PFO.

FIGS. 3A-3D show various orientations of PFOs.

FIGS. 4A-4D show how a treated PFO may not be fully sealed.

FIGS. 5A-5F show various treated regions that successfully seal the PFO.

FIG. 6 shows a balloon properly positioning a closure device withrespect to a layered tissue defect such as a PFO.

FIGS. 7A and 7B show tapered elongated members or a tapered balloon onthe distal end of a catheter used to position the catheter.

FIG. 8 shows a dual layer balloon in a layered tissue defect.

FIGS. 9-9A illustrate how expandable mechanical elements may be used toproperly position a closure device at a layered tissue defect.

FIGS. 9B-9D show expandable mechanical elements on a catheter shaft.

FIGS. 10A-10B show an alternative embodiment of expandable mechanicalpositioning elements.

FIG. 11 shows how radiopaque markers on a flexible wire may be used toposition a catheter and estimate tissue defect size.

FIG. 12 shows an alternative embodiment of a treatment device withflexible wires used for positioning and radiopaque markers for sizingand indicating treatment region.

FIG. 12A shows a crossing catheter with a guidewire lumen.

FIG. 13 is a cross-sectional view of a positioning device in the tunnelof a layered tissue defect.

FIG. 14 illustrates how whiskers on a catheter position the device andindicate the width of the tunnel entrance.

FIGS. 15A-15D shows a positioning device with retractable whiskers.

FIGS. 16A-16E illustrates a positioning device utilizing a looped wiredesign.

FIGS. 17A-17B show other features on the closure device housing thatfacilitate with positioning.

FIGS. 18A-18B illustrate a compound bend in the closure device thatassists with device positioning.

FIGS. 19A-19B show various embodiments of a bipolar positioning andsizing closure device.

FIG. 20 illustrates a closure treatment system.

FIG. 21 shows a closure treatment apparatus.

FIGS. 22A-22B illustrates an introducer sheath and hemostasis valve usedwith a closure treatment apparatus.

FIG. 23 illustrates a collapsing introducer.

FIGS. 24A-24E show how the collapsing introducer of FIG. 23 is used.

FIGS. 25A-25B show various aspects of the treatment catheter housing.

FIGS. 25C-25I show a bottom view of several housing and electrodeconfigurations.

FIGS. 26-36 show various ways a therapeutic element of a treatmentdevice can appose defect tissue.

FIG. 37 shows one embodiment of an apposition device.

FIGS. 38A-38D show an apposition device and how it apposes tissue.

FIGS. 39A-39F show how an apposition device and a closure treatmentdevice work together to close a layered tissue defect such as a PFO.

FIGS. 39G-39I show another apposition device and closure treatmentdevice working together to close a layered tissue defect such as a PFO.

FIG. 40 shows an apposition device comprising magnets.

FIG. 41 illustrates how magnets on either side of a PFO are used tobring the tissue layers together.

FIG. 42 shows magnets permanently implanted in order to close a PFO.

FIG. 43 shows additional features on the housing to help with tissueapposition.

FIGS. 44A and 44B show other features on the housing that help withtissue apposition.

FIGS. 45A-45C show a preferred embodiment of the closure device housing.

FIGS. 45D-45F show another embodiment of the closure device housing.

FIGS. 46-49A show various embodiments of electrode configurations.

FIGS. 50A-50B show a variable masking means.

FIG. 51 shows a means for actuating the variable masking of FIGS.50A-50B.

FIG. 51A shows a mesh electrode embodiment.

FIG. 52A-52B show a looped or petal electrode configuration.

FIGS. 53-54 illustrate various electrode embodiments.

FIG. 55 shows a bipolar configuration.

FIG. 56 shows a monopolar configuration.

FIG. 57 shows a preferred embodiment of the electrode.

FIG. 57A illustrates a hinged electrode with flexible connections to thehousing.

FIG. 58A-58C show the electrode disposed in a housing and a portion ofthe guidewire lumen exit aperture.

FIGS. 58D-58F illustrate various aspects of an electrophysiologicalmapping system combined with the closure treatment device.

FIG. 59 is a schematic representation of a closure treatment system.

FIGS. 60-67 are graphs illustrating energy algorithms.

DETAILED DESCRIPTION OF THE INVENTION

Devices, systems, and methods of the present invention generally providefor treatment of anatomic defects in human tissue, such as a patentforamen ovale (PFO), atrial septal defect (ASD), ventricular septaldefect (VSD), left atrial appendage (LAA), patent ductus arteriosis(PDA), vessel wall defects and/or the like through application ofenergy. The present invention is particularly useful for treating andfusing layered tissue structures where one layer of tissue at leastpartly overlaps a second layer of tissue as found in a PFO. Therefore,although the following descriptions and the referenced drawing figuresfocus primarily on treatment of PFO, any other suitable tissue defects,such as but not limited to those just listed, may be treated in variousembodiments.

I. PFO ANATOMY. As mentioned in the background section above, FIG. 1 isa diagram of the fetal circulation. The foramen ovale is shown PFO, withan arrow expanded view demonstrating that blood passes from the rightatrium RA to the left atrium LA in the fetus. After birth, if theforamen ovale fails to close (thus becoming a PFO), blood may travelfrom the right atrium RA to the left atrium LA or vice versa, causingincreased risk of stroke, migraine and possibly other adverse healthconditions, as discussed above.

FIGS. 2A-2I illustrate various PFO anatomies. For example, FIG. 2A showsthe secundum S overlapping with the primum P to form a frown line Fwhich is the entrance the PFO tunnel T and here, which is narrow andslightly offset. The PFO tunnel T may also be short and shallow asillustrated in FIG. 2B and cross-sectional view in FIG. 2C, or thetunnel T may be wide and long as shown in FIG. 2D. FIG. 2E andcross-sectional view FIG. 2F show a PFO tunnel T that is long. Other PFOtunnel T anatomies include an offset tunnel as in FIG. 2G, or aninitially wide tunnel T which narrows in FIG. 2H or an initially widetunnel T that narrows and is offset as illustrated in FIG. 21.

In addition to tunnel variations, the opening or frown F of the PFO andheight of the PFO limbus can also vary. FIG. 3A refers to anatomiclocations for FIGS. 3B-3D where superior points toward the head,inferior points toward the feet, posterior is toward the back of thebody and anterior is toward the front. FIG. 3B shows the overlap of theprimum P with the secundum S forming a frown line F which is theentrance to the PFO tunnel T. In FIG. 3B, the PFO tunnel T has ananterior orientation, while in FIG. 3C the PFO is inferior with ananterior tunnel T and FIG. 3D shows a superior PFO with a posteriortunnel T.

II. PLACEMENT. Given the anatomical variations of a PFO, using atraditional guidewire to guide a closure device to the defect fortreatment may not result in optimal placement all of the time. Forexample, in FIG. 4A, a traditional guidewire GW placed through a widePFO tunnel T may direct the closure device to a treatment region Tx thatonly includes a portion of the tunnel opening F, leaving an untreatedregion UTx that results in a leak L, as shown in FIG. 4B.

Similarly, as illustrated in FIGS. 4C and 4D, a single strand guidewireGW placed through a deeper PFO tunnel T that is somewhat offset, mayalign the device with the location of the tunnel T, but not let theoperator know that the device is not placed in a position to affect themouth or opening of the tunnel F, and may therefore result in a treatedregion Tx that falls short of sealing off the mouth of the tunnel,resulting in a leak path L.

Proper positioning is achieved when the closure device is placedoptimally in relation to the defect to deliver the desired closuredevice. Closure of the defect following accurate placement of the devicein a variety of PFO anatomies is illustrated in FIGS. 5A-5F. Thesefigures show the overlap of the primum P with the secundum S to form afrown line F which is the opening to the PFO tunnel T. Various treatmentregions Tx are shown which successfully close the PFO tunnel T. Accurateplacement allows the therapeutic device to be more precise, and inaddition, in the case of energy delivery catheters to seal the PFO,deliver the energy just to the opening on the defect so as to minimizethe location and amount of energy delivered to the heart tissue. Asillustrated in FIGS. 5A-5F, various electrode configurations andtreatment zones can be employed accurately with use of the presentinvention.

III. POSITIONING. In any of these procedures, a key aspect to performingclosure of an anatomic defect is positioning the catheter or treatmentdevice at the optimal location over the defect to be treated. Failure toplace the device in the optimal location can result in incompleteclosure of the defect, and require either a repeat application of theclosure mechanism, or an additional intervention (e.g. secondprocedure). For example if a traditional single strand guidewire isplaced through a PFO defect with a long tunnel, or a wide tunnel, it isdifficult to predict, where in that tunnel the guidewire is going toreside and therefore even if a closure catheter is tracked over the wirethat is through the PFO, it may not be directed to the center of thetunnel (in the case of a wide PFO), or to the mouth of the tunnel (inthe case of a longer PFO tunnel). Various other misalignments can alsooccur depending on the size, width, angle, and/or depth of the targeteddefect.

Various steps may be undertaken prior to performing a procedure to closea PFO, including sizing the defect, determining the orientation of thedefect, assessing the depth of the defect, and determining any relatedor adjacent anatomic features such as a septal aneurysm. PFOs can rangein size from about 1 mm to 30 mm although they are typically in therange from about 3 mm to 26 mm. Sizing of the defect could beaccomplished by placing gradations or markers on a sizing device or aseries of calibrated sizers could be utilized. Any of these can beadapted to be radiopaque or echogenic and therefore fluoroscopy,intravascular ultrasound, TEE, ICE and other visualization techniquesmay be employed to visualize and determine the foregoing so that thephysician can better determine how best to size and place the closuredevice to achieve closure of the defect. For example, radiopaque markersmounted on a balloon inflated in the PFO would permit the PFO tunneldiameter to be observed and estimated under a fluoroscope. Otherapparatus and methods for characterizing the tissue defect are describedherein.

In addition, these visualization techniques may be employed incombination with the intravascular devices of the present invention tonot only provide sizing information to the user, but in some casesprovide a mechanical guide or rail, over which to accurately place aclosure catheter. These features may be combined into one device, or aseries of devices to assess the geometry of the PFO, place and positiona closure device and ultimately deliver the closure therapy (clip,energy, sutures, etc.)

FIG. 6 illustrates a closure system 10 wherein a guiding member 12 suchas a catheter shaft or guidewire is inserted into the PFO tunnel Tcreated by the overlap of primum P and secundum S layers of tissue. Aninflatable member 14 such as a balloon mounted on the guiding member 12is then inflated thereby centering the guiding member 12 and closuredevice 16 with the tissue defect. The closure device may be advancedinto apposition with the tissue defect by pushing the closure system 10forward towards the defect, or a vacuum may be used to draw the tissuetoward the closure device. Other tissue apposition apparatus and methodsare discussed hereinafter. An example of a sizing/orientation apparatusis the PTS® Sizing Balloon Catheter available from NuMed, Hopkington,N.Y. The properly aligned closure device 16 can then successfully treatand close the defect. The combined apparatus allows sizing and or visual(radiographic, ultrasonic, etc.) feedback of PFO anatomy, as well asguiding features (such as over the wire placement of a closure catheter)so that closure catheters can be correctly positioned in the vicinity ofa PFO or other anatomic defect to deliver a variety of closure devicesincluding suture delivery catheters, clip delivery catheters, patchdelivery catheters, energy welding catheters and the like. Examplesclosure devices include, but are not limited to a suturing device asdescribed in U.S. Patent Publication 2005/0070923 (McIntosh); a clip inU.S. Patent Publication 2005/0119675 (Adams); a transeptal puncture inpublication WO 05/046487 (Chanduszko); a coil electrode in publicationWO 05/074517 (Chanduszko); a clip in U.S. Patent Publication2005/0187568 (Klenk); a transeptal puncture and electrode catheter inU.S. Patent Publication 2004/0243122 (Auth); and a gathering clip inpublication WO 05/027753 (Brenzel); the full disclosures of which areincorporated herein by reference.

Another embodiment of a positioning device is shown in FIGS. 7A and 7B.In FIG. 7A, positioning device 20 comprises a guiding member 22 such asa catheter or guidewire with a tapered set of elongated members 24 nearthe distal tip 26 of the device. The positioning device 20 may then beadvanced into the PFO tunnel and it is automatically centered as thetapered elongated members engage the tunnel walls. In addition topositioning, the device also facilitates sizing of the defect. A closuredevice may then be introduced over the guiding member 22 so that it isproperly positioned and a closure treatment is then applied to thedefect. In another embodiment shown in FIG. 7B, a positioning device 30comprises a catheter 34 having an expandable member 36 such as a balloondisposed near the distal end of the device. The expandable member isexpanded in the PFO tunnel resulting in the centering of the positioningof the device. Radiopaque markers 38 are disposed on the balloon 36allowing a physician to size the defect and observe position. Onceproperly positioned, a closure device is then delivered over thepositioning device to the defect so that a closing treatment may beapplied. The tapered elongated members 24 from FIG. 7A may also beincorporated into this embodiment to assist with positioning of thedevice. The catheter 34 may also have a guidewire lumen to allow use ofa guidewire 32.

With reference now to FIG. 8, a dual layer balloon is used to positionand size the tissue defect. A positioning device 40 has an inner balloon44 and an outer balloon 46 mounted on the distal end of a catheter 42.The catheter 42 is advanced into the tunnel of a PFO and the innerballoon 44 is then inflated until it engages the walls of the of tunnel,thereby centering the device in the tunnel. The outer balloon 46 maythen be inflated with contrast media and holes 48 in the outer balloonallow contrast media to weep out 50. Hole geometry may be varied toprovide appropriate contrast flow rates. This may be observed underfluoroscopy and therefore the tissue defect anatomy and dimensions canbe estimated including tunnel length, as well as allowing verificationthat the device is properly positioned. A closure device is thenintroduced over the positioning catheter to the defect and a closuretreatment is applied. Visualizing the contrast media also helps toverify that the closure device is properly positioned with respect tothe defect prior to treatment.

Another embodiment of a mechanical expansion device used for positioningis shown in FIGS. 9 and 9A-9D. In FIG. 9, a closure system 60 isillustrated having a catheter 62 with mechanical positioning elements 66in the collapsed position, mounted on the distal end of the catheter 62.The catheter 62 and positioning elements 66 are advanced into the tunnelT of the PFO and then the mechanical elements 66 are expanded until theyengage the defect walls and the device is positioned as illustrated inFIG. 9A. A closure device 64 also disposed on the catheter 62 istherefore also simultaneously positioned against the tissue defect andthen a treatment can be applied to close the PFO defect. FIG. 9A showsthe closure system when the mechanical elements 66 are expanded andengaged with the PFO tunnel, T.

FIGS. 9B-9D illustrate how the mechanical expansion elements 66function. In FIG. 9B the mechanical elements 66 are unexpanded andremain in a low profile position against the catheter 62. When thecatheter 62 is actuated as shown by the arrows in FIG. 9C, themechanical expansion members 66 flex and bow outward to variousdiameters depending on how far the catheter 62 is actuated. In FIG. 9Cfour expansion members are illustrated, although more or less may beemployed, as shown in FIG. 9D where two members are shown. The expansionmembers may be fabricated from polymers or metals having a spring temperor superelastic alloys such as nitinol.

Another mechanical expansion embodiment is shown in FIGS. 10A and 10B.In FIG. 10A, a positioning device 70 comprises a catheter 72 which isintroduced into the tunnel T of the PFO defect. Expansion members 74 arethen expanded thereby properly positioning the device within the tunnel.In this embodiment, the expansion elements 74 are retractable intoopenings 76 in the catheter. The expansion elements 74 are actuateddirectly to control their expansion, and when unexpanded, have an evenlower profile than the embodiment of FIG. 9C.

With reference now to FIG. 11, a positioning device 80 may includesingle or multiple flexible members 84 with both ends fixed to anelongate member such as a catheter 82. A part of the catheter shaft 85may act as a core member between the flexible members 84 to further addrigidity to the positioning device 80 to assist with its pushabilitytoward and through a tissue defect. The positioning device 80 may bedeployed through a closure device, or through a separate introducercatheter that is then removed, leaving the positioning device in place.Radiopaque markers 86 or coatings may be placed on various segments ofthe flexible members 84 to allow the user to view the orientation andspacing of the flexible members 84 and correlate them to the defectanatomy. For example, markers may be useful on the widest point of theflexible members to show the width of the PFO frown or opening, F, andmay also continue along the length of the flexible members to helpdelineate the tunnel T (e.g. see the angle, show tunnel width, etc.). Atleast a portion of the flexible members are preferably placed betweenthe tissue of the PFO with the main catheter 82 extending into orthrough the defect tunnel. The flexible members 84 extend laterally fromthe main body of the catheter to provide definition of the outer edgesof the PFO, transitioning to define the location (angle) and size orwidth of the defect tunnel. The radiopaque markers 86 in FIG. 11 arevisible under fluoroscopy and permit orientation of the defect andlocation of the frown or opening to be discerned based on observation ofthe geometry of the flexible members placed within the defect.

FIG. 12 shows how a treatment device may be used with a positioningdevice. In FIG. 12, a closure treatment catheter 90 has an elongateshaft 92 and a housing 100 on the distal end. A treatment region 96 isdisposed within the housing 100 and radiopaque markers 98 outline thetreatment area 96. A positioning device 94 is advanced to a layeredtissue defect such as a PFO until the distal end 104 extends beyond thedefect. Flexible elongate members 106 delineate the tunnel of the PFOand radiopaque markers 102 allow the physician to see the defect underfluoroscopy. The closure treatment catheter 90 is then advanced over thepositioning device 94 until the radiopaque markers of treatment region98 are aligned with the radiopaque markers 102 of the positioning deviceand it is clear that the treatment catheter 90 is positioned over thedefect properly for treatment. The positioning device 94 may then beremoved and a closure treatment can then be applied to the defect toclose the layered tissue defect. If the treatment device 90 is placeddirectly over the positioning device 94, the positioning device 94 ispreferably constructed so that it can be removed with the treatmentdevice 90 left in place. For example, in this embodiment, it ispreferable that the flexible elongate members 106 can be pulled backthrough a lumen of the treatment device 90.

FIG. 12A shows a crossing catheter similar to the embodiment describedin FIG. 12 above. In FIG. 12A, the crossing catheter 1300 is also usedwith a positioning device. Here, the crossing catheter 1300 has anelongate shaft 1310 and a housing 1308 on the distal end of the shaft.An inner lumen shown by dotted lines is axially disposed within thecrossing catheter elongate shaft 1310 and has an exit port 1312 in thehousing. The crossing catheter 1300 is used with a positioning device1314 that is advanced to the layered tissue defect (such as a PFO) untilthe distal end 1304 extends over the defect. The positioning device 1314has flexible elongate members 1306 that mark the boundaries of thetissue defect. In the case of a PFO, the flexible elongate members 1306indicate the tunnel of the PFO and radiopaque markers 1302 permit aphysician to observe the defect under fluoroscopy. Once the positioningdevice 1314 has been delivered, the crossing catheter 1300 is thenadvanced over the positioning device 1314 until the housing 1308 isdisposed over the tissue defect as indicated by the radiopaque markers.A vacuum may then be applied to the crossing catheter, either via theinner lumen or another lumen so that the housing 1308 is apposed withthe tissue defect. Once apposition is obtained, the positioning device1314 may be removed and a treatment device, or a guidewire over which atreatment device may be delivered, may be advanced axially along thecatheter elongate shaft 1310 through the inner lumen or another lumenuntil the distal end of the treatment device exits the inner lumen port1312. For example, the inner lumen port may be curved laterally suchthat, in the case of placing a guidewire, the guidewire exits the innerlumen at an angle sufficient to direct the guidewire transeptally, orthrough the tissue of the layered defect (for example from right atriumto left atrium either through the primum, through the secundum orthrough both tissue structures as depicted in FIG. 38B hereinbelow).Once the guidewire is placed transeptally and centered optimally withrespect to the defect, a closure catheter may be passed over theguidewire such that it may be deployed across the atrial septum at apoint that is substantially centered, or positioned to close the PFO.For purposes of this disclosure, “centered” or “positioned” may bedescriptors of how the crossing catheter is optimally positioned toguide a transeptal puncture device in order to position a separatetreatment catheter at the position on or over the tissue defect suchthat when a closure device is deployed, it substantially closes thedefect. Once the layered tissue defect is repaired, the closuretreatment device and crossing catheter may then be removed from thetreatment site.

FIG. 13 shows a cross-sectional view of a portion 114 of a positioningdevice 110 in a PFO tunnel. A portion of the positioning device 110extends past the tunnel exit 116, while the proximal end of the deviceis outside of the tunnel, 112. FIG. 14 shows another embodiment of apositioning device. Positioning device 120 represents a guidewire withwhiskers 126 at the distal end to seat the wire device through a PFO andalso to assist in sizing the width and locating the tunnel entrance ormouth F. The whiskers 126 may be fabricated from a pre-formed resilientmaterial (e.g. nitinol, spring temper steel, Elgiloy®, formed or coiledstainless steel wire) such that when the guidewire is deployed from acatheter, the whiskers 126 deploy outwardly to seat within the cornersof the PFO tunnel T. Once in place, the closure device can be trackedover the guidewire 122. The closure device may include radiopaquemarkers that can be aligned with guidewire markers (not shown) to seatover the outer limits of the width of the PFO and to include the tunnelentrance. Once in place the guidewire can be removed through theguidewire lumen in the closure device. In the case of the whisker wire,the whiskers would flex upwards to be in line with the main wire and allbe pulled out through the guidewire lumen. Additionally, the whiskerelements may be spring loaded to ensure that they extend out to thefarthest width of the defect that they are measuring or positioning. Itis also within the scope of the invention that the guidewire device maybe a separate catheter and while it provides a visual docking target,the closure catheter and the guidewire/positioning catheter are notphysically linked, but are placed separately from each other.

FIGS. 15A-15D shows one embodiment of the whiskers positioning devicediscussed above with respect to FIG. 14. In FIG. 15A, a positioningdevice 130 has a sheath housing 136 with slits 138. A positioningcatheter 132 lies in the sheath 136 and positioning whiskers 134 alsoremain covered by the sheath 136. Once the positioning device 130 isplaced within a PFO, the whiskers 134 may be released from the sheath136, and the whiskers then expand through the slits 138 in the sheath136, as shown in FIG. 15B. The whiskers 134 spring to a fully deployedposition thereby properly positioning the device 130 and allowing PFOsizing, shown in FIG. 15C. Once the positioning device 130 is no longerrequired, the whiskers 134 may be retracted into the sheath 136 which isillustrated in FIG. 15D.

In another embodiment shown in FIGS. 16A-16C, a looped wire design isemployed. In this embodiment, a looped guidewire type of positioner isused to position the device. In FIG. 16A, a closure device 140 has anelongated catheter shaft 142 and a distal housing 150. A treatmentregion 144 is disposed on the housing 150 along with placement wireapertures 146 and a guidewire aperture 148. The looped guidewire in FIG.16B with high flexibility is retractable into apertures 146 and can beextended into the defect in a looped configuration to form a sizing andpositioning device, as well as serving as a rail over which closuredevice can be placed accurately at a treatment site. In FIG. 16C, thelooped wire 154 is advanced until it engages the walls of the layeredtissue defect. A guidewire 148 may also be used to help deliver theclosure device 140 to the tissue defect, and it exits out of aperture148. FIG. 16D shows how the guidewire 152 and looped wire 154 fit into aPFO tunnel T and position the closure device housing 150 over theentrance of the defect, F. The looped wire 154 may be designed withvariable stiffness along its length to facilitate sizing andpositioning. For example, the looped wire 154, shown in a straightenedout configuration in FIG. 16E may have a stiff section 156 foraccommodating the widest PFOs, a less stiff section 158 adjacent to thestiffest section 156 and a flexible section 159 in the middle of theloop wire.

Additional catheter features may also be employed in order to aid inplacement and sizing. For example, in FIG. 17A, a closure device 170 hasa retractable catheter shaft 175 with a housing 176 attached to thecatheter shaft 175. The housing 176 has a treatment region 174 on thehousing and extensible positioning rails 178 serve as feelers to helpstabilize the treatment device 170. The housing 176 and positioningrails 178 are retractable into sheath 172. Alternatively, the housingshape may be modified to include an extended nose 179 as seen in FIG.17B. This shape helps position the closure device 170 against the tissuedefect. A moveable guidewire lumen (not shown) may also be used tofacilitate placement and sizing. A compound bend can also help theclosure device to be properly positioned adjacent to a tissue defect asshown in FIG. 18A. In FIG. 18A, several bends 194, 196 in the shaft 192of a closure device 190 help to properly position the treatment portionof the device 190 against the tissue defect. In FIG. 18A, typical rangesfor the first bend indicated by angle α is up to 75° while a second bendindicated by angles β and γ are up to 60° and 75° respectively. FIG. 18Bshows a back view of the of the treatment device shaft where angles θand Δ both typically can range up to positions that encompass a range upto 80°.

In an alternative embodiment, a wire sizing, positioning and treatmentdevice may also include an electrode or multiple electrodes for applyingenergy to the defect while it is in position or near the position toclose the defect. The electrode may be formed or treated to beradiopaque to assist in sizing of the defect. Wire forms the bipolarelectrode configurations, and sizes, orients and applies energy to closethe defect. In FIG. 19A, a wire sizing, positioning and treatment device210 is placed in a PFO. Wires 218 and 220 position the device 210 withinthe tunnel, and also serve as electrodes. A radiopaque marker band 214may be employed to indicate device position and vacuum lumens 216 mayalso be employed to allow the treatment device to approximate the defectsurfaces prior to, during or following the application of sealingenergy. In an alternative embodiment, FIG. 19B shows a design where theelectrodes 234, 236 are modified on positioning, sizing and treatmentdevice 230 with tips 238 that help the device to be removed afterapplication of energy without disturbing the weld created.

IV. CATHETER DEVICE. Referring now to FIG. 20, in an exemplary catheterdevice 250 which may be modified according to the present invention fortreating an anatomic tissue defect includes an elongate catheter shaft260 having a proximal end 264 and a distal end 266, a sheath 256 (or“sleeve”) optionally disposed over at least part of shaft 260, a handle268 coupled with a proximal end of sheath 256, and a housing 262 coupledwith catheter shaft distal end 266. A distal opening 272 for opposingtissue, an electrode 274 (or other suitable energy transmission memberin alternative embodiments for transmitting radiofrequency (RF) energyto tissues, attachment members 276 (or “struts”) for coupling electrode274 with housing 262 and for providing support to housing 262, andradiopaque markers (not shown) for coupling attachment members 276 withhousing 262 and/or catheter body distal end 266 and for facilitatingvisualization of device 250. A guidewire 280 is passed through catheter250 from the proximal end through the distal end. In the embodimentshown, catheter body proximal end 264 includes an electrical couplingarm 282, a guidewire port 284 in communication with a guidewire lumen(not shown), a fluid infusion arm 286 in fluid communication with theguidewire lumen, a suction arm 289 including a suction port 294, a fluiddrip port 288, and a valve switch 290 for turning suction on and off.

Fluid drip port 288 allows fluid to be passed into a suction lumen toclear the lumen, while the suction is turned off. A flush port withstopcock valve 298 is coupled with sheath 256. Flush port and stopcockvalve 298 allows fluid to be introduced between sheath 256 and catheterbody 260, to flush that area. Additionally, sheath 256 has a hemostasisvalve 296 for preventing backflow of blood or other fluids. The distaltip of the sheath also has a soft tip 258 for facilitating entry andrelease of the catheter housing 262 during delivery. The catheter device250 also includes a collapsing introducer 300 partially disposed inhandle 268.

The collapsing introducer facilitates expansion and compression of thecatheter housing 262 into the introducer sheath 256. By temporarilyintroducing the collapsing introducer sheath 300 into introducer sheath256 the catheter housing 262 may be inserted into introducer sheath 256and then removed, thereby allowing the introducer sheath 256 toaccommodate a larger housing 262 without having to simultaneouslyaccommodate the collapsing introducer 300 as well. The collapsingintroducer 300 also has a side port for fluid flushing 302 and a valve(not shown) prevents fluid backflow. Locking screw 292 disposed in thehandle 268 may be tightened to control the amount of catheter shaft 260movement. Finally, an energy supply 254 is connected to the catheter viathe electrical coupling arm 282 and a controller 252 such as a computeris used to control energy delivery. In operation, it may also bepossible to de-couple the handle from the device if desired, or toremove the handle altogether.

FIG. 21 illustrates the treatment catheter device 350 only. Thetreatment catheter 350 has an elongate catheter shaft 366 having adistal end 354. A housing 352 on the distal end of the catheter shaft354 delivers a treatment to a layered tissue defect to close the defect.The catheter shaft 366 is axially aligned with a handle 372 and exits ata proximal end of the device and is sealed with a hemostasis valve 378to prevent fluid backflow. An energy connector 380 and flush port 379are also disposed on the proximal catheter end along with a vacuum port376 with additional port 377. A screw 374 tightens the catheter shaft366 within the handle 372 to minimize motion between the two. Acollapsing introducer tube 368 with soft tip 364 and flush port 370 isalso disposed partially in the handle 372 and is used to collapse thehousing 352 and introduce it into an introducer sheath 358. Theintroducer sheath 358 also has a soft tip 356 which helps to accommodateand collapse the housing 352 when it is being withdrawn back into theintroducer sheath 358 for removal from the body. A radiopaque marker mayalso be placed near the soft tip 356 to assist in visualization during atreatment procedure using fluoroscopy. Both the collapsing introducer368 and the introducer sheath 358 have side ports 370, 362 for flushing.Valves in the collapsing introducer (not shown) as well as a hemostasisvalve in the introducer sheath 360 prevent blood or other fluids frombackflowing.

FIG. 22A shows the introducer sheath preferably used in the closuretreatment system of FIG. 20. In FIG. 22A, introducer sheath 400 has anelongated shaft 404 which is used to introduce the closure treatmentdevice into the human body. The introducer sheath 400 in FIG. 22A isshown as an elongated sheath, however the sheath may be angled or bentin different directions to assist with placement of the closuretreatment device. The introducer sheath 400 has a soft distal tip 402and may include a radiopaque marker, which helps to accommodate thelarger size distal end of a treatment catheter and collapse it into thesheath during removal as well as facilitate visualization underfluoroscopy. A side port 408 with one or more flush ports 412 and astopcock valve 410 is also useful for flushing the introducer sheath anda hemostasis valve 406 prevents blood or fluid backflow when thetreatment catheter is placed in the sheath. FIG. 22B illustrates oneembodiment of the hemostasis valve, where two silicone disks 416 areused to create the hemostasis valve membrane 414. In FIG. 22B thesilicone disk 416 is then scored partially through the top surface andalso partially through the bottom surface, but not all the way throughthe disk. Two score lines are created 418, 419 transverse to oneanother. At the intersection of the score lines 417, the silicone diskis punctured all the way through. This permits a catheter distal tip topenetrate the silicone disk and when it is advanced further, the scorelines separate enough to accommodate the catheter while maintaining aseal. In preferred embodiments, the silicone disk is approximately0.352″ in diameter and the slit widths can accommodate and seal over a16 F shaft.

The collapsing introduce 420 is illustrated next in FIG. 23. Collapsingintroducer 420 has an elongate section 424 which can accommodate adistal treatment catheter housing. By collapsing the housing in thecollapsing introducer, it can then be easily introduced into theintroducer sheath previously described. The distal tip of the collapsingintroducer is soft to help accommodate the larger size treatmentcatheter housing. In a preferred embodiment, the collapsing introducerhas a length approximately 6 inches and its soft tip is fabricated withPebax polymer having a durometer of, for example, 35D while the elongatesection 424 comprises, for example Pebax 72D durometer. Other relativedurometers may also be used in the scope of the present invention tofacilitated collapse of the catheter housing, while still providingflexibility and torqueability of the catheter shaft. While currentlyillustrated as round, the soft tip may also be oval, crescent moon, orasymmetrically crescent shaped to facilitate collapsing the housing. Theproximal end of the collapsing introducer has a hemostasis valve 428designed to accommodate the treatment catheter shaft as well as a flushport 426.

FIGS. 24A-24E illustrate how the collapsing introducer works. In FIG.24A, a treatment catheter 450 is inserted into the collapsing introducer452. In FIG. 24B, the collapsing introducer 452 is slidably movedtowards the distal end of the treatment catheter 450 until the housing460 is collapsed and enclosed by the collapsing introducer 452. Thetreatment catheter 450 with its housing 460 collapsed in the collapsingintroducer 452 is then advanced and introduced into an introducer sheath462 in FIG. 24C, and the collapsing introducer 452 is pulled back, sothat the housing 460 is released from the collapsing introducer 452 butstill is constrained by the introducer sheath 462. In FIG. 24D thetreatment catheter 450 is advanced forward into the introducer sheath462 until the housing 460 exits the introducer sheath 462 and resumesits shape. The treatment catheter is advanced to a layered tissue defectand a treatment is then applied. After the treatment is competed, thecatheter housing 460 is pulled back into the introducer sheath 462 andthe catheter 450 may be removed from the patient's body.

In alternative embodiments as described in detail below, additionalfeatures or fewer features may be included on catheter device 250. Forexample, a number of modifications may be made to catheter body distalend 266 in accordance with different aspects of the invention. Some ofthese may include lubricious liners or coatings on the device as well asheparin coatings for reducing thrombus. Different configurations forfluid delivery and vacuum are also possible. Additionally, a controllerbuilt into the power generator can alleviate the need for a computercontroller, except for displaying treatment parameters. Therefore, thefollowing description of embodiments is intended to be primarilyexemplary in nature and should not be interpreted to limit the scope ofthe invention as it is described in the claims.

V. Optimizing Tissue Apposition

A. Housing Design and Other Tools. One aspect of a successful tissueweld of a defect to be treated, is the interface of the tissue at thetherapeutic element (electrode, heating element, or mechanical closingmechanism). This interface may be impacted by the following variables,including any leaks in the housing, leaks or shunts in the anatomy (e.g.through the PFO), physical placement of the housing over the defect,deformation of housing against tissue interface and resulting housingvolume, forces exerted by the housing, and the pressure used to apposethe treatment site with the housing. Various embodiments are presentedthat may assist in tissue apposition within or against the treatmentelement for closing a PFO or other layered tissue defect. These designsmay be used in conjunction with any of the defect closure devicesdescribed in the co-pending cases which have been previouslyincorporated by reference. Particularly, closure catheter devices suchas those detailed in the co-pending application Ser. Nos. 10/873,348;10/952,492; and 11/049,791 may be enhanced by the following features.

Housing designs that maintain a sufficient chamber and features to gripand appose the tissue of the defect, and maintain the seal of thetherapeutic element at the tissue interface may be desirable. Arepresentative embodiment of a catheter housing 475 is shown in FIG.25A. The housing 475, is attached to a catheter shaft 477 and is formedfrom 60A durometer silicone because of its high tear strength andresistance to deformation at the temperatures employed to weld tissue.Other durometers may also be employed and in some cases a housing may beconstructed of multiple durometer polymers in one device, or a polymerand a reinforcing element such as mesh or a filament. The housing 475has a primary shape 476 and a surface 479 adapted to appose the tissuedefect. However, upon application of vacuum through a lumen 480 in thecatheter shaft 477, the housing may still flatten or collapse 478.Similarly, skirt or flange of the housing can flatten as well. This canlead to a shallower (shallower) housing volume within which tissue maybe apposed. As such, certain features may be designed into the housingto define the optimum housing volume.

Some features that provide a more resilient housing, and in turn allowgreater tissue invagination upon vacuum activation, include: reinforcingthe roof of housing, taller housing, and reinforcements in flange orskirt of housing. As depicted below, areas of the housing may beselectively reinforced to aid in sealing the treatment area within thedevice housing. In particular the “roof” of the housing may be formed ofa thicker material (preferred material is silicone and it would bemolded, the mold cavity would be constructed to allow more material toflow into the reinforced region). The reinforced roof allows the housingto remain somewhat tented during vacuum apposition. For the roofreinforcement, a stiffening element, such as spring steel or nitinol maybe used in thicknesses ranging from, for example between 0.002″-0.005.″Reinforcement in the roof region may also be achieved by molding athicker region using the material of the housing, or adding material tothe roof of the housing to make the reinforced area in the range of0.005″ to 0.025″ thick, for example 0.010″ thick while stillaccommodating vacuum channels as described in copending application Ser.No. 10/952,492, the full disclosure of which has previously beenincorporated by reference, and allowing the housing to collapse. Some ofthese features are incorporated into the embodiment of FIG. 25B. In FIG.25B, the housing 485 comprises a reinforced region 490 in the roof 488of the housing 485.

At the midpoint of the housing between the main housing and the flange,stiffening elements 492 or extensions 496 may be employed in a similarmanner (e.g. additional molded material or separate resilientextensions). For example, such extensions or reinforcement may have athickness of between 0.005″ to 0.050″ and between 1-3 mm in height.

In addition, a semi-rigid ring 494 may be incorporated into the bottomof the flange to give hoop strength to the flange, especially whenvacuum is applied via a lumen 487 in the catheter shaft 486 connectedwith the housing 485. In certain embodiments, a 1 mm.times.1 mm squarein cross-section of material was molded at the bottom of the flange. Inanother embodiment, a nitinol ring was used, allowing the thickness ofthe region to be about 0.010″ or slightly smaller and not square incross-section which allows for better collapsibility. In certain otherembodiments, a polymer O-ring may be employed. Such additional housingmaterial and reinforcement elements may be used alone or in combinationwith each other for the desired rigidity, while still allowing thehousing to be collapsed within a guide catheter for deployment to andretrieval from the treatment site. The housing element 485 may beadapted to appose the tissue and keep it in place while a fusing orfixation element is brought into contact to secure the tissue. Forexample, the housing element 485 may be activated (suction applied) andthen a catheter device containing a clip or fixation element may beadvanced to the treatment site, and applied to the apposed tissue.Examples of fixation elements may be clips such as those described inpending application Ser. No. 10/787,532 (Attorney Docket No.022128-000130US), filed Feb. 25, 2004; and Ser. No. 10/811,228 (AttorneyDocket No. 022128-000400US), and further U.S. application Ser. No.10/948,445 (Publication 2005/0070923) to McIntosh, U.S. application Ser.No. 10/856,493 (US Publication 2004/0249398) to Ginn, and PCTpublication WO/04/069055 to Frazier, the full disclosures of which areincorporated herein by reference.

Other housing configurations adapted to appose a layered tissue defectsuch as a PFO are illustrated in FIGS. 25C through 25I, which shows abottom view of the housing that apposes the tissue defect. For example,in FIG. 25C, a housing 1320 has a boomerang shaped side 1322 with a noseextending from the triangular apex region that may provide betterapposition with certain tissue defects. FIG. 25D shows a triangularshaped side 1342 of the housing 1340 with apices radiused while FIG. 25Eillustrates a kidney bean shaped side 1362 of the housing 1360. FIG. 25Fshows a circular housing side 1382 while FIG. 25G depicts a housing 1400with a generally triangular shaped side 1402 but with the base and apexmodified to include nose-like protrusions. FIGS. 25H and 25I also showvariations on the triangular shaped side of the housing for tissueapposition. In the case where an electrode is used to close the layeredtissue defect, the electrode shape may match the housing or it may bemodified to best match the tissue defect. FIGS. 25C through 25I showvarious electrode embodiments that may be used.

A cone shaped or domed housing can provide greater tissue apposition,(optionally in combination with a “stepped” electrode as set forth inapplication Ser. No. 10/952,492, the full disclosure of which haspreviously been incorporated herein by reference). An example of thestepped electrode 504 may be seen in housing 500 of FIG. 26. Theelectrode may alternatively be planar and optionally may be angled inthe housing to accommodate tissue thickness variations. This isillustrated as electrode 530 in housing 525 of FIG. 27.

A hinged housing may also provide better tissue apposition and defectclosure by allowing the housing to better adapt to anatomical variationsin the tissue defect. In one embodiment shown in FIG. 26A, a treatmentdevice 1450 comprises an elongated catheter shaft 1454 with a housing1452 adjacent to its distal end. The housing has a hinge mechanism 1456that allows the housing to articulate. When the housing articulates, itsshape adjusts to better conform with the anatomy of the tissue defect.In FIG. 26A, an apposition surface 1462 is operatively coupled with thehousing so that it too can better conform to the tissue defect anatomy.The apposition surface 1462 may only comprise a surface for appositionor may additionally comprise a treatment region that can be used toclose the layered tissue defect. Furthermore, optional separate vacuumports 1458 and 1460 may be located in the housing to assist the housingappose the tissue defect. In FIG. 26A, vacuum ports 1458 and 1460 arepositioned within the housing so that they may help draw in the primumand secundum tissue layers for better apposition in a PFO defect.

In another embodiment shown in FIG. 26B, multiple hinges 1484 areutilized in the housing 1486 of a treatment device 1480. An elongateshaft 1482 is connected to the housing 1486 and may be used toarticulate the housing into different configurations with control rodsor wires. The hinges may also be adapted to permit flexing of thehousing when it is pressed against a surface. An apposition surface 1488which generally takes the same form as apposition surface 1462 in FIG.26A is also operatively connected to the housing 1486 so that its shapemay be adjusted for better apposition with the tissue defect. FIG. 26Cillustrates how the hinged housing 1506 of a treatment device 1500provides an alternative apposition surface 1508. Furthermore, vacuumports 1524, 1526 may be used in the housing 1522 of a closure device1520, as illustrated in FIG. 26D. Here, vacuum ports 1524 around thecircumference of the housing 1522 are combined with a centrally placedvacuum port 1526 for enhanced apposition of the housing 1522 against thetissue defect.

In alternative embodiments, a screen or slotted member may receivetarget tissue and oppose or “grip” the tissue during treatment. Thescreen may also be an electrode (monopolar/bipolar). FIG. 28Aillustrates the primum P and secundum S tissue layers of a PFO beingreceived into a screen upon application of vacuum through a lumen 556 ina catheter shaft 554 connected with the housing 552. In this embodiment,the screen is also an electrode with an electrical connector 560 runningthrough a lumen 556 in the catheter shaft 554. A cross-sectional view ofthe tissue 568 being received into a screen 564 having a receivingaperture 566 is shown in FIG. 28B. FIG. 29A illustrates another way inwhich tissue P, S can be captured by the screen 584 and FIG. 29B shows across-sectional view of the tissue P, S being received by an aperture588 in the screen 590. The screen 590 may also serve as an electrode toweld the tissue layers together or a secondary electrode may be deployedlater during the procedure for welding.

A recess in housing (or around skirt) 604 may assist in opposing orgripping tissue once the tissue is brought into the housing 600 using avacuum. The screen 606 may be fixed to position tissue, or may bemoveable as shown by the arrows in FIG. 30. Movement is controlled by anelongate member 610 through a lumen 612 in the catheter shaft 608 tofurther clamp tissue P, S against the recess 604, and the screen 606 maybe an electrode. This embodiment is illustrated in FIG. 30.

In another embodiment shown in FIG. 31, a first screen 633, usually withlarge interstices, may be employed together with a second screen 632.The second screen 632 is moveable between a first position and a secondposition as shown by arrows, or range of positions, relative to thefirst screen 633 and can be employed to trap the tissue P, S prior totreatment. Ideally, such screens 632, 633 could also be the electrode(s)for applying energy to join the tissue flaps of the heart defecttogether. They may be monopolar (one screen is energized while the otheris totally insulated), or bipolar (wherein both screens are energized tocreate a bipolar energy field to assist in tissue fusing.

As shown in FIG. 32, the housing 652 may be actuated to further griptissue with the recess feature 664 previously described above. Grippingaction of the housing pivots the housing from one position 662 to asecond position 664 and can be employed by actuatable struts (not shown)within housing material that extend from a pivot point at the apex ofthe housing, or by advancing a sheath (not shown) over the housing 652to further collapse the structure on the tissue P, S.

FIG. 32A illustrates an alternative approach to apposing tissue. In FIG.32A, a moveable vacuum tube 671 is advanced in order to appose tissue P,S. Once vacuum is applied and the tissue is engaged, the vacuum tube 671may be pulled back into the housing 666 so that tissue is engagedagainst a screen 667 which can also serve as an electrode. FIG. 32Bshows that the vacuum tube 668 may have an optional vacuum screen 670 atits distal end to facilitate tissue engagement.

In a further embodiment depicted in FIG. 33, a bipolar clamping device(electrode structure) 680 may be integrated into the housing 676, oradvanced as a separate element to grasp and weld the tissues P, S of theheart defect together. In one embodiment, the bipolar clamping element680 may be deployed distally of the catheter housing to grasp the defectto be treated and draw it back into the housing for treatment. In thisembodiment, such clamping graspers 680 may be employed separately or inconjunction with suction applied through a lumen 682 connected with thehousing 676. The graspers 680 are controlled by an elongate member 684through a lumen 682 in the catheter shaft 678. The suction operates tomaintain a seal in the treatment area, and the clamp 680 can operate tonot only clamp the tissue, but also to keep the treatment catheter 675positioned at the site of the defect.

FIG. 34A shows another embodiment where a ring electrode 712 may beemployed in the housing 702 or around the flange of the housing (724 inFIG. 34B) to seal tissue. In the case of the ring electrode 712 in thehousing 702, it can either be fixed to the walls of the housing, orseparate and deployable about the acquired tissue. FIG. 34A shows thering electrode 712 separate from the housing 708. In some cases it maybe desired to cinch the electrode from a larger diameter 710 to asmaller diameter 712 around the tissue P, S, such as a snare typedevice. In the case of the ring electrode 724 around the flange of thehousing 722 depicted in FIG. 34B, the electrode structure can provideadditional rigidity to the flange region, thereby assisting with tissueapposition while also being activated to delivery energy and seal.

Further, the ring electrode in either configuration (cinched/snare ringor ring on outer housing) may be the return electrode in a bipolarsystem as shown in FIG. 35. In FIG. 35, a second active electrode 748may be inserted into the tissue to be treated P, S while a ringelectrode 744 is disposed within the housing 742 and serves as thereturn electrode. FIG. 36 shows an alternative embodiment where a secondactive electrode 768 is inserted into the treatment region P, S and acinch or snare electrode 770 is the return electrode.

With reference now to FIG. 37, an additional embodiment shows anapposition device 780 of the present invention which may include amechanical device 784 deployed from the housing 782, through the tissueor defect to be treated (see FIG. 38B), and capable of pulling thetissue back into apposition with the housing 782. Such a mechanicalassistance device 784 can be used alone or in conjunction with vacuumapposition. The apposition device 784 would be very low profile in its“stowed” condition for placement through tissue of the defect or throughthe defect opening, and then deployed to an expanded condition asindicated by phantom lines, whereupon it may be drawn back toward thecatheter housing 782 to tension the tissue between the catheter housing782 (and electrode) and the expanded portion of the apposition device.One embodiment of this device shown in FIG. 38A includes a molly bolttype (or mallecott) apposition device 810 deployed through a needle 804placed through defect or through defect tissues. The device is shownplaced through tissue in FIG. 38B. Once placed through tissue, it isthen expanded 808 to provide a backstop and hold tissue, and isillustrated in FIG. 38B. In yet another embodiment the apposition devicemay be a wire that expanded to a looped or “petal” type configuration812 as shown in FIG. 38C and a side view in FIG. 38D. In any of theseembodiments, the apposition device may be deployed through the guidewirelumen of the treatment device, or through a separate, dedicated lumen.These devices may be positioned with respect to the defect to be treatedby using the positioning devices of the present invention describedpreviously.

In a further embodiment, an apposition device may be deployed separatelyfrom the treatment device into the left atrium, remote from thetreatment site, to “bookend” the defect against treatment catheter andthereby create enhanced tissue apposition. Such a separately deployedapposition device would preferably be low profile to allow the remotepuncture site to heal naturally, without requiring a therapeuticintervention to close the puncture. FIGS. 39A-39E illustrate this withrespect to a PFO closure, but several other defects in the heart couldbe apposed and closed in a similar manner. In FIG. 39A a needle cannula826 is inserted from the right atrium to the left, remote from thedefect opening. A tissue apposition device 828 is then deployed into theleft atrium toward the site of the defect or tissues to be apposed, asshown in FIG. 39B. A treatment catheter 832 and the left atrialapposition member 834 are then brought into alignment at the site of thedefect to be closed, which is illustrated in FIG. 39C. Force is appliedto assist in apposing the tissue closely within the housing 830 of thetreatment device 832, shown in FIG. 39E. Once the defect is closed, thetreatment device 832 is removed and the apposition device 836 isretracted into the needle cannula 826, after which time the needlecannula 826 is removed and nothing is left on the left atrial side ofthe heart. The needle cannula entry site may be left to close naturallyand the layered tissue defect is also closed as seen in FIG. 39E.Another embodiment is shown in FIG. 39F where a needle like structure843 is used to penetrate the tissue defect. An apposition member 842 isthen released from the needle structure 843 to provide a backstop. Apivot on the device 841 can then be actuated, bringing the treatmenthousing 840 and backstop 842 together. The closure treatment may then beapplied. After the closure treatment is completed, the backstop 842 maybe retracted into the needle structure 843, and both are withdrawn intoa sheath 844, and the entire device is removed from the patient or movedto another treatment location.

FIGS. 39G-39I illustrates another embodiment for enhanced appositionincluding a elongated guidewire 1530 with a flexible T-shaped distal end1532. In FIG. 39G, the elongated guidewire 1530 is placed through thePFO tunnel until the T-shaped end exits the tunnel on the left side ofthe heart. The flexible whiskers 1532 which form the T-shaped end arethen free to expand outwardly and then can serve as an anchor point forthe guidewire 1530. In FIG. 39H, the elongated guidewire 1530 isretracted which results in the whiskers 1532 forcing the primum Pagainst the secundum S, thereby reducing the gap therebetween andpermitting better fusing of the two layers. A closure treatment device1534 is then delivered to the treatment site, here, delivery of theclosure treatment device 1534 is advanced axially over the guidewire1530. The closure treatment device 1534 then applies a treatment to thetissue defect, partially closing the defect, except for the region wherethe guidewire 1530 rests. In FIG. 391, after a partial closure of thedefect is obtained, the guidewire 1530 is removed from the tunnel andthe closure device 1534 may complete the treatment by sealing the PFOand fusing the primum P and secundum S together 1538.

Using a similar technique, another approach to applying the requiredtissue compression prior to defect closure utilizes magnetic attractionas shown in FIGS. 40-42. By placing magnets or electromagnets on eitherside of the layers of tissue that require apposition, a compressiveforce can be applied without requiring a physical link between the sidesof the tissue. Any combination of ferromagnetic material, magnetmaterial, and/or electromagnetic material can be used to create thedesired force. While not required, the use of rare earth permanentmagnets such as Samarium Cobalt (SmCo) or Iron-Neodymium (NdFeB) providesubstantial levels of magnetic flux for a given volume of material andare implantable grade materials. Coupling such a magnet with aferromagnetic counterpart can simplify the use of magnetic attraction tocreate force because orientation of the ferromagnetic portion of thecoupling does not require a specific orientation relative to thepermanent magnet in order to create an attractive force. Further, use ofan electromagnet can be beneficial since it can be selectively activated(turned on and off).

The magnet and/or ferromagnetic components used for such an applicationcan be in singular elements, or an array of smaller elements that may bemore easily delivered to a remote location through a patientsvasculature. For example, magnetic components 856 may be coated orformed for implant in a human body, loaded into a catheter 852 as shownin FIG. 40. The assembly 850 may be delivered to relevant locationswhile contained, and then released at the desired location with respectto the defect to be treated, and deployed.

Alternatively, as shown in FIG. 41, magnetic elements 862, 864 areplaced on either side of a PFO (one in the right atrium and one in theleft atrium). An energy treatment catheter 866 is placed between themagnets 862, 864 in the right atrium to deliver the tissue weldingtreatment once the tissue or brought together by the magnetic force.Optionally, the magnet on the right atrium 862 could be incorporatedinto the energy treatment catheter. In this embodiment, the magneticdevice deployed in the left atrium 864, could be placed with a similarneedle catheter delivered remote from the defect to be treated, and oncemagnetic apposition was achieved and the defect closed, the left sidemagnetic 864 component would be removed.

It is also within the scope of the present invention, as shown in FIG.42, to permanently implant a magnetic coupler 875 to close the anatomicdefect. The magnetic coupler would have a first magnetic element 876placed on the left side of the defect, and a second magnetic element 878placed on the right side of the defect. One or more inflatable balloonsmay be used as deployment tools, for example to separate each magneticelement until proper positioning is obtained. Once each element isproperly placed, the balloon can be deflated and removed, leaving themagnetic coupling elements in place, and able to attract each other toseal the defect.

B. Isolating Treatment Site. The ability to appose tissue and create atreatment area conducive to welding tissue may be enhanced by theapplication of negative pressure, i.e. vacuum, at the treatment site. Inaddition, it may be desirable to infuse fluid into the treatment sitefor a variety of reasons.

Sealing. Certain features of the housing may be constructed to assist increating a robust seal at the tissue interface, and maintaining thatseal for the duration of the treatment. To balance the housing featuresthat allow for greater tissue apposition (e.g. a more resilienthousing), the following features may be incorporated into the housingflange.

Additional “grippers” or protrusions 894 in the rim of housing 892increase tissue apposition to the device 890. An additional vacuum lumen896 in the housing rim 892 may also be useful to distribute the vacuumforce toward the outer edge of the housing at the housing/tissueinterface. This is illustrated in FIG. 43.

Alternatively, as illustrated in FIG. 44A, the location of the grippers908 and the additional vacuum port 906 may be reversed. Furthermore, agusset 904 may be added to the housing 902 to increase the sealing forceof the flange, but still keep the housing flexible. Gussets 924 may beplaced circumferentially around the outer housing flange 922 at variouslocations, and this is seen in FIG. 44B.

FIGS. 45A-45C show a preferred embodiment of the housing 940. FIG. 45Aillustrates a top view of the housing which preferably has a flange orskirt 942 having a diameter of 0.921 inches and the housing itself has adiameter 944 of 0.730 inches. An elongate member 950 represents thetransition from the housing 940 to a catheter shaft. The housing has aslightly tapered profile when observed from the side in FIG. 45B. Thedistal tip of the housing 946 is the lowest point of the taper, andpreferably has a height of 0.140 inches while the proximal end of thehousing 948 is higher and is preferably 0.297 inches high. A front viewof the housing is seen in FIG. 45C and this view shows the flange orskirt 942 connected to the housing 944.

Another embodiment of the housing is illustrated in FIGS. 45D-45F. InFIG. 45D, a top view of the housing 1550 is shown. The housing 1550 herehas a nose-like front projection 1552 and a rectangular-shaped 1554 rearprojection. The housing is typically attached to an elongate cathetershaft 1556. Both projections 1552 and 1554 form a skirt around thehousing 1550, attached along the housing rim 1558, and that helps thehousing to match the tissue defect anatomy and appose the defect. FIG.45E is a side-view of housing 1550 showing the skirt 1564 and a domedhousing top 1562. A front view of the housing 1550 is shown in FIG. 45Fwhich illustrates the skirt 1552 attached with the housing rim 1558.

Infusate. Successful welds of heart defects may be achieved in thepresence of infusate or drip fluids into the treatment region, asdescribed in application Ser. No. 10/952,492, the full disclosure ofwhich has previously been incorporated herein by reference, to mediatethe moisture content of the treatment area and maintain patency of thecatheter lumens. Infusate is used primarily to prevent blood fromstagnating within a treatment device distal housing and therebyclotting. By providing constant infusate flow, stagnation is avoided.Heparin can also be added to the infusate to further minimize clotting.Alternatively, welds of heart defects have also been achieved withrelatively “dry” tissue (low or little infusate).

For example, in the event that the use of an infusate is desired, thefollowing variables may affect the efficacy of the tissue weld, namely,type of infusate (saline, D5W (Dextrose 5% and water) or G5W (Glucose 5%and water), rate of infusion, flow distribution at tissue interface(pattern, consistency), temperature of infusate and the like. In anexemplary range, infusion may be used in the following range 0-30ml/min, and more particularly in the range of 1-10 ml/min. The infusateis then aspirated from the treatment site via the vacuum lumen. Thevacuum suction creates a continuous draw of flush through the infusionlumen, passing through the distal housing, and back out the vacuumlumen, for example a passive or “closed loop” infusion. The infusate isthen collected in a vacuum canister. Operation and further detail on theinfusion of fluid can be found in related application Ser. No.10/952,492 (Attorney Docket No. 022128-000220US), incorporated herein byreference. Adequate vacuum seal can be determined by observation of thedistal housing under fluoroscopy (lack of movement, “flattening” asdetermined by imaging of fluoroscopic markers or echogenicity ofhousing), and observation of the color of the fluid suctioned to thevacuum canister (e.g. by a change from blood to clear fluid as thedominant fluid suctioned to the vacuum canister (fluid changed from redto clear). Although a complete seal is desirable, an example of asubstantial seal that may still include an “acceptable leak rate” is inthe range of 0-150 ml/min, for example, in the range of 1-30 ml/min.This leak may be attributable to physiologic phenomena, as well asmechanical issues with the housing seal against the tissue.

C. Energy Application for Defect Closure: Electrode Design and EnergyAlgorithm Various parameters can be controlled to achieve the mostadvantageous result in closing a PFO or other defect in the heart withenergy. As discussed above, greater tissue apposition can function toincrease the likelihood of consistently welding the PFO tissues (primumand secundum), in a clinically acceptable procedure time. In addition togreater tissue apposition, various parameters related to the poweralgorithm can be controlled and optimized. Certain parameters includedeveloping a feedback loop to ensure enough power is delivered toachieve the desired closure (plane of welding), that the power deliverydoes not lead to unwanted “pops,” that the power delivery does not leadto impedance spikes of the kind that prohibit additional power deliveryto tissue within the specified procedure time, and the like. Othersinclude design of the electrode, including the size, thickness and otherphysical features that effect energy delivery. The treatment device andthe power system of the present invention are depicted in FIG. 20 wherethe power supply 254 hooks into port 282 with a standard medicalelectrical connector.

Electrode Design. The configuration of the electrode may play a role inoptimum energy delivery. Certain features of an electrode or heatingelement that may affect closure (welding) include, element density,geometry, size, current density, surface features (gold plating forradiopacity, coatings, electropolishing of conductive surfaces),location of the power connection, and points of insulation on theelement.

For example, a larger electrode, although able to treat a greater areaof tissue, requires more power and therefore is less efficient, and maylead to additional conduction in the tissue to areas of the heart thatthe procedure is not intended to effect. An electrode design that ismatched (size, capacity) to provide “localized energy density” to theintended treatment region can function to limit the power required toachieve the intended result, and therefore a more efficient, saferlesion is created.

For example, in FIG. 46, a banded electrode 964 may be adapted toconcentrate the power delivery at the point over which the defect comestogether. This band can either be created by cutting an electrodepattern that is in the desired shape or masking a larger electrode suchthat only the desired band of active electrode is exposed. In FIG. 46,banded electrode 964 is cut into a rectangular shaped piece with aguidewire exit port 966 running through the electrode 964. Various otherportions around the electrode and housing are insulated 962 so thatenergy is only delivered over the banded electrode 964. Additionally,openings within the electrode 972 allow vacuum to be applied for tissueapposition and struts 970 connect the electrode 964 to the housing 968and help provide support. FIG. 48 shows an alternative embodiment of thebanded electrode 1028 wherein the active electrode band pattern has beencut into the desired shape, here an undulating wave-like pattern.Additional features such as an exit port for a guidewire 1032, vacuumports 1030, a thermocouple 1026, insulated struts 1024 for support and ahousing flange 1022 have previously been discussed.

FIGS. 47 and 49 on the other hand employ the masking embodiment. In FIG.47, portions of the electrode are masked 996 so that energy is onlydelivered via an active region 999. Other features such as vacuum ports994, support struts 998 are also utilized. FIG. 49 shows a variation ofmasking, where portion of the undulating wave-like pattern previouslydiscussed above are masked to control energy delivery. In FIG. 49,masking 1044 controls where the active electrode region is. Typicalelectrode measurements are in the range of 30 mm wide by 20 mm tall, forexample 15 mm wide by 9 mm tall. The total area of the electrode mayvary depending on the chosen geometry. Electrodes may be configured in avariety of shapes, including elliptical, circular, rectangular,triangular, or have geometries that are a combination of thoseapproximate shapes in order to best fit the geometry of the tissue to betreated. An alternative electrode embodiment is illustrated in FIG. 49A.In FIG. 49A, a housing 1570 is disposed on distal end of an elongatecatheter shaft 1576. The housing 1570 has a nose-like protrusion 1572and a rectangular shaped rear protrusion 1574. The nose-like protrusion1573 may also be moved closer to the electrode 1586, as shown by dottedline 1573, in order to better appose the tissue. A partially oval shapedelectrode 1586 is disposed in the housing 1570 and a guidewire lumen1578 port 1580 exits through the electrode 1586. The electrode 1586 isadapted to more accurately match PFO anatomy. In the case of a PFO, theelectrode is adapted to treat PFOs ranging in size from 1 mm to 30 mmand more typically in the range from 3 mm to 26 mm.

Masking may be applied by spraying or dip coating and typically employsa silicone layer, although other methods and materials are well known inthe art. Alternatively, it may be desirable to design the maskingelement on the distal catheter housing such that it can be variablewherein the mask opening only exposes the desired amount of septaltissue to the chosen form of energy. The opening may be round, oval orother shapes, such as a crescent, to mimic the defect to be treated.Illustrative embodiments of this are shown in FIGS. 50A and 50B. Forexample, FIG. 50A shows a variable mask wherein the inner diameter 1056can be controlled, while in FIG. 50B an elliptically shaped aperture1074 is controllable.

In operation and illustrated in FIG. 51, a treatment catheter 1090 maybe formed by using coaxial shafts 1092, 1094 that allow relative axialrotation to twist an elastomeric tube 1096 or otherwise create a valvedeffect (similar to an iris valve). Final mask shape is then achieved byrotating one shaft relative to the other until the desired mask shape isreached. The two shafts can then be locked together to prevent the shapeof the mask from changing during treatment.

In a further embodiment, a mesh electrode 1097 is shown in FIG. 51A, andmay be employed, having an insulation coating 1098 or sleeve. In use,tissue would be drawn into the cavity created by the electrode andenergy delivered. Alternatively, the insulating sleeve may be withdrawn,exposing the desired amount of active electrode.

FIG. 52A illustrates a further embodiment of an electrode having lobesor “petals” 1104 which may be employed to the desired size, either byusing separate loops, or feeding out a length of preformed nitinol wireto achieve the desired configuration. Because an electrode such as thiscan be deployed once a seal by the catheter housing 1102 has beenobtained, it is possible for the user to apply a certain amount ofdirectional force with the electrode against the tissue, which may beuseful in creating optimal tissue apposition with the target, on itsown, or in conjunction with other apposition devices and techniquesdisclosed herein. A bottom view of the housing 1102 emphasizing thepetals 1104 is seen in FIG. 52B.

In a further example and with reference to FIG. 53, the active electrodemay be an alternating current bipolar electrode (requiring less energy,and in a more localized manner), and configured as either an electrodecommensurate with the size of the housing, or less than the size of thehousing, by masking, otherwise insulating, or cutting the electrode to asmaller size. Interdigitating active 1122 and return 1124 electrodes canbe laid out on a planar electrode substrate. Alternating active 1142 andreturn 1144 electrodes across a planar electrode substrate may also beemployed as seen in FIG. 54.

The use of RF energy to generate a weld of a defect in conjunction withthe use of a magnetic coupler to create opposing force could allow theRF system to be either monopolar or bipolar depending on theconfiguration. For example as depicted in FIG. 55, each half of themagnetic couple 1162, 1164 could be one pole of a bipolar RF circuit. Inaddition, only one of the portions of the magnetic couple 1184 is usedas part of a monopolar RF circuit and this is illustrated in FIG. 56.Further combinations that include either one or more of the componentsof the magnetic couple in either a monopolar or bipolar RF circuit arealso possible. It is within the scope of the present invention to alsosize, mask or otherwise modify the electrode configurations described inco-pending application Ser. No. 10/952,492, previously incorporatedherein by reference.

A preferred electrode embodiment is shown in FIG. 57. An electrode 1200is illustrated prior to attachment with a catheter housing. Here, struts1204, 1206, 1208 extending from the electrode are designed forattachment to the housing in order to connect the structures with oneanother. Struts 1204, 1206 and 1208 also serve to provide support forthe housing. Barbs 1202 may be employed on the struts 1204 and 1208 tohelp attach them to the housing. A monopolar electrode is formed from aseries of parallel bars 1222 separated by a slit 1224. A set of bars1222 is separated from an adjacent set of bars by another gap 1218. Anouter perimeter is formed by a ring 1216 and apertures 1226 allow vacuumto be applied as well as administration of an irrigation fluid. Tabs1210, 1211 and 1212 allow a piece of tubing to be attached to theelectrode to facilitate guidewire entry and exit from the housing. In apreferred embodiment, not intended to be limiting, the electrode has athickness of approximately 0.0029 inches and struts 1204, 1206 and 1208are typically about 0.020 inches wide by 0.004 inches thick. Ring 1216width is about 0.012 inches, while the bar 1222 width is approximately0.040 inches and slits 1224 are about 0.012 inches with gaps 1218 beingabout 0.030 inches wide. The slits in this embodiment allow suction tobe applied through the electrode, help to minimize tissue from adheringto the electrode surface and create an edge from which RF energy isdelivered to tissue.

A floating electrode embodiment is illustrated in FIG. 57A. In thisfigure, an electrode 1600, unattached with a catheter housing is shown.Struts 1604, 1606 and 1608 are connected with the housing and help toprovide support to the housing during tissue apposition and/or vacuumapplication. Barbs 1602 on the struts 1604 and 1608 also help to connectthe struts 1604 and 1608 to the catheter housing. A parallel series ofbars 1622 is separated by a slit 1624 therebetween, forming a monopolarelectrode. Each set of parallel bars 1622 is separated from an adjacentset off bars by another gap 1618 and an outer perimeter is formed by aring 1616. The electrode bars 1622 connect with the perimeter 1616 via aflexible elastomeric coupling 1628 such as silicone. The flexiblecouplings 1628 allow the electrode to float and therefore the electrodecan adapt to various tissue defect anatomies more effectively bycompensating for changes in tissue thickness or height. Additionally,the electrode bars 1622 are hinged 1630, allowing further adjustabilityof the electrode surface to accommodate are more diverse range of tissueanatomies. Other aspects of this electrode embodiment include apertures1626 within the electrode which allow vacuum to applied as well asadministration of irrigation fluid. Tabs 1610 and 1612 allow tubing tobe attached to the electrode to facilitate guidewire entry and exit fromthe housing. Electrode dimensions generally take the same form as theelectrode described in FIG. 57 above.

FIG. 58A shows the electrode of FIG. 57 mounted in a catheter housing1260. The housing 1260 has a flange 1256. Struts are embedded in thehousing and therefore, only the electrode 1254 is exposed. An aperturefor a guidewire is more clearly visible in FIG. 58A and is representedby 1258. FIG. 58C illustrates a piece of tubing 1262 used to transitionfrom the guidewire aperture 1258 into the guidewire lumen of thecatheter shaft 1252 in FIG. 58A. The tubing is a length polymer tubewith two apertures adapted to be placed over tabs 1210 and 1212 in FIG.57 to secure the tubing to the electrode. Tab 1212 may also be bent atan angle to further facilitate guidewire entry and exit from theguidewire aperture 1258. FIG. 58B highlights the two apertures on thetubing. In a preferred embodiment, not intended to be limited, thistubing is approximately 0.044 inch outer diameter.times.0.039 inch innerdiameter polyimide with a length about 39 inches. The long aperture 1264is approximately 0.687 inches from the distal tip of the tubing and hasa width of about 0.033 inches by 0.134 inches long and a radiusapproximately 0.017 inches. The smaller aperture 1266 is approximately0.038 inches by 0.028 inches.

In addition to applying energy for closure of a layered tissue defect,the electrodes of such a device can be designed to allowelectrophysiology monitoring of the heart. Such mapping would permit aphysician to determine if the treatment device is too close to sensitiveareas of the heart, such as the AV node. Additionally, monitoring couldbe used to ensure that during treatment, aberrant conductive pathwayswere not being created. Mapping also allows power delivery to becontrolled so that minimal required power is delivered and also permitsthe active surface of the electrode to be controlled and minimized sothat treatment energy is not applied to an area greater than necessary.

As shown in FIG. 58D, two small circular electrode pairs 1654 may beplaced on and insulated from the electrode 1656 or housing 1652 and canserve as bipolar mapping electrodes. The electrodes may take a number ofconfigurations such as two pairs side by side in FIG. 58D or in a lineararrangement 1684 as shown in FIG. 58E. These electrodes 1694 may be 0.5mm to 2 mm in diameter as shown in FIG. 58F, and can be fabricated fromstainless steel although platinum or platinum-iridium are preferable aswell as nitinol. Cardiac electrophysiology mapping is well known in theart and is well documented in the medical and scientific literature.Exemplary products are manufactured by Boston Scientific.

Algorithm. In the treatment of a PFO in a human heart, the followingwelding algorithms may be successfully employed to achieve closure orsealing of the PFO tissues using a range of parameters that utilizefeedback to vary the time and power applied to achieve a tissue weld.The following are merely examples and not intended to limit the scope ofthe present invention. In a preferred embodiment, the algorithm wouldstart at a low power (e.g. 1-10 Watts to 20-50 Watts) and graduallyincrease over time. This allows the controller to evaluate how thedefect is responding to the application of energy. The objective of thealgorithm is to deliver the maximum amount of power during a desiredduration, while not over-treating the tissue. A software controllersystem may be employed to ramp the power over the designated time and torespond to the impedance readings or other user or manufacturerdesignated feedback or settings.

A schematic depiction of the power supply is depicted in FIG. 59. Thepower supply is connected to the treatment device and a return electrodeis connected to the generator. A variety of feedback inputs may also beconnected to the power supply or CPU, including thermocouples,electrodes for sensing impedance and the like. A software controllersystem utilizing a CPU can be employed to adjust the power over thedesignated time and to respond to the impedance readings (e.g. shutoff/restart/restart at lower or higher power as directed by the inputalgorithm). This system may be further linked to a computer (laptop) orother user interface for purposes of graphical interface and datacollection.

In one example of a tissue welding algorithm for PFO treatment, energymay be applied with an initial power setting of 20 Watts, and the powerincreased every 30 seconds by 5 Watts until 40 Watts is reached (“powerramp”). Following this initial ramp, energy may be applied untileither 1) a total run time of 10 minutes is reached, or 2) an impedancespike occurs. If the total run time reaches 10 minutes the applicationof power is considered complete for purposes of this example. If animpedance spike is reached, an additional power ramp is reapplied untila total of five spikes have occurred or until a subsequent spike occursafter a cumulative run time of 7 minutes. The power ramp of this orother embodiments may also be incremental, e.g. ramp increased over 30seconds, up to 5 Watts, until 40 Watts is achieved. Alternatively, thepower ramp may begin at 20 Watts, increased to 25 Watts and maintainedat 25 Watts until the application is complete (7-10 minutes), as shownin FIG. 60. The application of a similar algorithm in a different tissuesample, may produce results such as those below; the variations may bedue to tissue or other anatomical variations, as shown in FIG. 61.

In another example of ramping, the system operates to apply 15 Watts,ramped by 5 Watts every 30 seconds after initial 45 seconds, for 10minutes or first impedance spike after 7 minutes. The overall number ofimpedance spikes is limited to 5. The system in this example includespassive fluid infusion. A solution of D5W, or other fluids such asnormal saline may be employed for the infusion. An example of thistreatment using a banded electrode (see description of banded electrodeabove), is shown in FIG. 62.

In addition, it may be advantageous to alter the starting power, andtime between ramps, for example allowing additional time between stepups in power, for example 60 seconds. In the example below, the initialpower is 20 Watts, with a step up in power of 5 Watts every 60 seconds,to a maximum power of 40 Watts for a duration of 10 minutes. If animpedance spike is encountered, then applied power is reduced to 25Watts for the remaining time up to 10 minutes, as shown in FIG. 63.Following the initial spike, if the impedance reading does not exceedthe minimum impedance by 2 Ohms, the power can be ramped up to 35 Wattsfor the remainder of the procedure time, as shown in FIG. 64.

Alternatively, an algorithm where energy delivery is initiated at ahigher power (for example 50 Watts) and ramped down in response toimpedance spikes or “pops” may be employed as shown in FIG. 65. Forexample, power may be applied starting at 50 Watts, and a clinicallyacceptable procedure time followed (e.g. 5-15 minutes).

The power may then be reduced by 7 Watts each time the impedance spikesafter fewer than 2 minutes of power application (an impedance “spike” inthis example, is characterized by a rise in tissue impedance to about100 Ω). For example, if the power is set to 50 Watts and runs for 1minute 30 seconds before spiking, energy application is stopped, poweris reduced to 43 Watts and energy application is resumed. If the systemthen runs at 43 Watts for 3 minutes before spiking, the energyapplication is stopped only briefly before being reapplied at 43 Wattsagain. If there are spikes during the application of power, this processis repeated until a maximum cumulative run time of between 6 and 12minutes is reached. If there is a spike after a cumulative run time of 6minutes, the application of power is considered complete. If there is nospike, the energy application is continued at a power setting of 50Watts for a maximum of 12 minutes.

An example of application of pulsed power is depicted in FIG. 66A usinga banded electrode. Forty (40) Watts of power was applied in 15 secondpulses, and temperature and impedance were monitored and charted. InFIG. 66A each power application consisted of approximately 5 seconds ofwarm-up where the impedance dropped, after which the impedance resumedwhere it left off from a previous power application. FIG. 66B depictsthe same power application as FIG. 66A however the chart reflects thedata with the 5 seconds of warm-up in each application of energy(included in the graph of FIG. 66A) removed.

In a preferred embodiment of the algorithm, power is delivered inmultiple power runs or frames. In the first frame, RF power is set to 20Watts and power is increased by 5 Watts every 60 seconds until a maximumof 40 Watts is obtained. If during this frame, impedance inflects andthen returns to at least its initial value or appears to be reaching aspike then power is turned off. If power has been delivered for morethan 7 minutes, application of power is terminated and a cool down stepis initiated. If power has been delivered for less than 7 minutes, thenadditional power is applied after a 30 to 120 second pause.

In the second power run or frame, if RF energy was delivered for 180seconds or less during the first run, the second frame may be started at15 Watts. If the impedance has not exceeded its minimum from the secondframe by 2Ω after 90 seconds, power is increased to 25 Watts. If afteranother 90 seconds, the impedance has not exceeded its minimum from thesecond frame, power is again increased to 35 Watts. If the impedanceinflects and then returns to at least its initial value (of the currentframe) or if impedance appears to be reaching a spike, power is turnedoff. Similar to the first frame, if power was on for more than a totalof 7 minutes, power is turned off and the cool down step is initiated.If power has been run for a total of fewer than 7 minutes, thenadditional power should be applied in the third power run after waiting30 to 120 seconds.

If more than 180 seconds of RF was delivered during the first frame thenRF power is applied at 25 Watts. If the impedance has not exceeded itsminimum from the second frame by 2Ω after 90 seconds, power is increasedto 35 Watts. If the impedance inflects and then returns to at least itsinitial value (of the current frame) or appears to be reaching a spike,power is turned off. If power has been delivered for more than a totalof 7 minutes, the power is turned off and the cool down step isinitiated. Otherwise, if power has been delivered for fewer than 7minutes, then additional power should be applied in a third power run,after waiting 30 to 120 seconds.

In the third power frame, RF power is applied at the last setting usedin the second frame, e.g. either 15, 25 or 35 Watts. If impedanceinflects and then returns to at least its initial value (of the currentframe) or appears to be reaching a spike, power delivery is terminatedand the cool down step is initiated.

In all power frames, when total power delivery time reaches 10 minutes,power is turned off and cool down is initiated. During cool down, RFpower delivery is stopped and tissue temperature is monitored. Tissue isallowed to cool down for at least 30 seconds or until tissue temperatureis 40° C. or lower before moving the treatment device.

In FIG. 67, the preferred algorithm is utilized. Here, the firstapplication of power was less than 3 minutes therefore the secondapplication was initiated at 15 Watts, instead of 25 Watts. There arestill power spikes if the impedance is stagnant, as shown in FIG. 67,where power is increased to 25 Watts because the impedance did notexceed its minimum by 2 Ohms after 90 seconds. If the impedancecontinued to remain stagnant, then after another 180 seconds, there ispotential for another increase in power up to 35 Watts.

In all cases, power is applied at least once, but may be appliedadditional times, in this example at most, three times, although powermay be delivered to help “burn off” and remove the electrode from thetissue. Power may range from 100 Watts down to 10 Watts, for examplefrom 50 Watts down to 25 Watts. The total energy delivered to achieve aweld employing any of the algorithm examples above, or any variationsthereof may be in the range of 1,000 joules to 50,000 joules, in thecase of a PFO weld, a possible range of 6,000-15,000 joules.

Algorithm—Other Approaches, Adjustments. It is within the scope of thepresent invention to modify the parameters of the algorithm to achievethe desired tissue weld, to account for a number of variables, such asthose described earlier in this disclosure. For example, treating a PFOwith a thin primum may require longer application of power, higherpower, or a higher ramp of power, given the potential for energydissipation through the thinner tissue. Treating a different defect suchas a ASD or LAA may require bringing tissues together that result in athicker sample to weld, and therefore the treatment may utilize lesstotal energy or lower applied powers, for example 5-35 Watts, or mayinclude additional applications of power at multiple regions along thedefect to be sealed.

In addition, an algorithm utilizing a bipolar treatment device such asthose described earlier, may use a ramping algorithm such as that setforth above, but may utilize less power somewhere in the range of 1-25Watts, for example 5-10 Watts and more particularly 2-3 Watts in somecases. Treatment times for bipolar application can range from 1-20minutes.

Although the foregoing description is complete and accurate, it hasdescribed only exemplary embodiments of the invention. Various changes,additions, deletions and the like may be made to one or more embodimentsof the invention without departing from the scope of the invention.Additionally, different elements of the invention could be combined toachieve any of the effects described above. Thus, the description aboveis provided for exemplary purposes only and should not be interpreted tolimit the scope of the invention as set forth in the following claims.

1. An apparatus for fusing a layered tissue structure, the apparatuscomprising: a catheter body having a proximal end and a distal end; ahousing on a distal portion of the catheter body; and an energytransmission member associated with the housing, wherein the energytransmission member is configured to distribute energy over apredetermined pattern.
 2. An apparatus as in claim 1, wherein the energytransmission member is disposed over an opening in the housing.
 3. Anapparatus as in claim 2, wherein the energy transmission member isadapted to allow the housing to appose the layered tissue structure. 4.An apparatus as in claim 1, wherein the energy transmission member iscollapsible.
 5. An apparatus as in claim 1, wherein the energytransmission member has an active surface.
 6. An apparatus as in claim5, wherein the energy transmission member further comprises an inactivesurface.
 7. An apparatus as in claim 5, further comprising anon-conductive mask region which defines the active surface.
 8. Anapparatus as in claim 1, wherein the energy transmission member has avariable active surface region.
 9. An apparatus as in claim 1, whereinthe energy transmission member is an electrode.
 10. An apparatus as inclaim 9, wherein the electrode is adapted to penetrate tissue.
 11. Anapparatus as in claim 1, wherein the energy transmission member has ageometry which substantially approximates the layered tissue structureto be treated.
 12. An apparatus as in claim 11, wherein the energytransmission member geometry is adapted to treat a patent foramen ovaleranging in size from about 1 mm to about 30 mm.
 13. An apparatus as inclaim 11, wherein the energy transmission member geometry comprises aband.
 14. An apparatus as in claim 13, wherein the band geometry isselected from the group consisting of elliptical, circular, rectangular,triangular and combinations thereof.
 15. An apparatus as in claim 13,wherein the band geometry comprises an undulating wave-like pattern. 16.An apparatus as in claim 11, wherein the energy transmission membergeometry comprises a mesh.
 17. An apparatus as in claim 11, wherein theenergy transmission member geometry comprises one or more lobes.
 18. Anapparatus as in claim 11, wherein the energy transmission membergeometry comprises one or more bars.
 19. An apparatus as in claim 18,wherein the bars have a length and a width and wherein the bar length isgreater than the bar width.
 20. An apparatus as in claim 18, wherein thebars have a first region and a second region, and wherein the first andsecond regions are hingedly connected.
 21. An apparatus as in claim 18,wherein the bars have a first region and a second region, and whereinthe first and second regions are oppositely charged regions adapted todeliver bipolar energy.
 22. An apparatus as in claim 21, wherein thebars interdigitate.
 23. An apparatus as in claim 21, wherein theoppositely charged regions alternate.
 24. An apparatus as in claim 18,wherein some of the bars are substantially parallel to each other. 25.An apparatus as in claim 24, wherein the bars comprise at least oneopening therein.
 26. An apparatus as in claim 25, wherein the at leastone opening is a slit disposed between the bars.
 27. An apparatus as inclaim 26, wherein the bars have a width and the slit has a width that isless than the width of the bars.
 28. An apparatus as in claim 24,further comprising a guidewire lumen axially disposed in the catheterbody and wherein the guidewire lumen has a distal exit port disposedbetween the bars.
 29. An apparatus as in claim 28, further comprising aramp adjacent to the distal exit port.
 30. An apparatus as in claim 28,wherein the guidewire lumen passes through the housing.
 31. An apparatusas in claim 24, wherein the bars are adapted so that a vacuum may beapplied through the bars.
 32. An apparatus as in claim 24, wherein thebars are adapted so that tissue adherence to the bars is minimized. 33.An apparatus as in claim 24, wherein the bars are adapted to create asmooth interface with the layered tissue structure.
 34. An apparatus asin claim 24, wherein the bars are adapted to form an edge from whichenergy is delivered.
 35. An apparatus as in claim 1, wherein the energytransmission member is biased toward a proximal portion of the housing,thereby maximizing the physical distance between the AV node of theheart and an active electrode portion of the energy transmission memberpositioned over the layered tissue structure to be treated.
 36. Anapparatus as in claim 7, wherein the non-conductive mask is connectedwith the active region and forms an insulated region between the housingand the energy transmission member.
 37. An apparatus as in claim 1,wherein the energy transmission member is plated or coated for enhancedelectrical characteristics.
 38. An apparatus as in claim 1, wherein theenergy transmission member is coated for enhanced radiopacity.
 39. Anapparatus as in claim 1, wherein a guidewire port is disposed adjacentto the energy transmission member.
 40. An apparatus as in claim 1,wherein the energy transmission member is adapted so that a vacuum maybe applied through the energy transmission member.
 41. An apparatus asin claim 1, wherein the energy transmission member comprises strutswhich connect the energy transmission member to the housing.
 42. Anapparatus as in claim 1, wherein an elastic element flexibly connectsthe energy transmission member with the housing.
 43. An apparatus as inclaim 1, further comprising a thermocouple adjacent to the energytransmission member.
 44. An apparatus as in claim 1, wherein the housingis adapted to allow fluid delivery to the region of the layered tissuestructure when the housing is apposed with the layered tissue structure.